Criminalistics: An Introduction to Forensic Science about Harold Shipman Questions

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WILL EXTEND DEADLINE 6 ADDITIONAL HOURS IF NEEDED Answer each question minimum of 400 words. Must use provided material (PDF book) as well as additional sources to help support answers. Remember to use in-text citations in each new paragraph. Reference/cite in APA format. DO NOT PLAGIARIZE. Here is the reference for the PDF: Saferstein, Richard (2014) Criminalistics: An Introduction to Forensic Science, 11th edition.


1.) Use the Internet to research Harold Shipman (aka Dr. Death), the English doctor who is estimated to have killed over 236 of his patients.

2.) What was Shipman's murder weapon of choice and how did this weapon allow him to go undetected for so many years?

3.) Based on your research, what did you determine to be Shipman's motive for the murders?

4.) As lead prosecutor, determine what evidence or facts the police overlooked that could have ended this case sooner. Would those facts and evidence have been enough to convict Dr. Shipman?

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chapter 9 matter, light, and glass examination Learning Objectives L I D D E L L , After studying this chapter you should be able to: T t Define and distinguish the physical and chemical properties of I matter F t Define and distinguish elements and compounds F and gas t Contrast the differences among solid, liquid, A t Understand how to use the basic units of the metric system N t Define and understand the properties of density and Y refractive index t Understand and explain the dispersion of light through a prism 1 t Explain the relationship between color and the selective 5 absorption of light by molecules 6 t Understand the differences between the wave and particle 8 theories of light T S t List and explain forensic methods for comparing glass t Describe the electromagnetic spectrum ISBN: 978-1-323-16745-8 fragments t Understand how to examine glass fractures to determine the direction of impact for a projectile t Describe the proper collection of glass evidence KEY TERMS amorphous solid atom Becke line birefringence Celsius scale chemical property compound concentric fracture crystalline solid density dispersion electromagnetic spectrum element Fahrenheit scale frequency gas (vapor) intensive property laminated glass laser liquid mass matter periodic table phase photon physical property physical state radial fracture refraction refractive index solid sublimation tempered glass visible light wavelength weight X-ray Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 204 CHAPTER 9 physical property The behavior of a substance without alteration of the substance’s composition through a chemical reaction. chemical property The behavior of a substance when it reacts or combines with another substance. The forensic scientist must constantly determine the properties that impart distinguishing characteristics to matter, giving it a unique identity. The continuing search for distinctive properties ends only when the scientist has completely individualized a substance to one correct source. Properties are the identifying characteristics of substances. In this chapter we will examine properties that are most useful for characterizing glass and other physical evidence. However, before we begin, we can simplify our understanding of the nature of properties by classifying them into two broad categories: physical and chemical. Physical properties describe a substance without reference to any other substance. For example, weight, volume, color, boiling point, and melting point are typical physical properties that can be measured for a particular substance without altering the material’s composition through a chemical reaction; they are associated only with the physical existence of that substance. A chemical property describes the behavior of a substance when it reacts or combines with another substance. For example, when wood burns, it chemically combines with oxygen in the air to form new L substances; this transformation describes a chemical property of wood. In the crime laboratory, a routine procedure for determining the presence of heroin in a suspect specimen is to react itI with a chemical reagent known as the Marquis reagent, which turns purple in the presence of heroin. D This color transformation becomes a chemical property of heroin and provides a convenient test for its identification. D E The Nature of LMatter Before we can apply physical properties, as well as chemical properties, to the identification and L comparison of evidence, we need to gain an insight into the composition of matter. Beginning , building block of all substances—the element—we will exwith knowledge of the fundamental tend our discussion to compounds. T Elements and Compounds matter All things of substance; matter is composed of atoms or molecules. element A fundamental particle of matter; an element cannot be broken down into simpler substances by chemical means. periodic table A chart of elements arranged in a systematic fashion; vertical rows are called groups or families, and horizontal rows are called series; elements in a given row have similar properties. A pure substance composed of two or more elements. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 compound Matter is anything that has mass I and occupies space. As we examine the world that surrounds us and consider the countless variety of materials that we encounter, we must consider one of humankind’s most remarkable F accomplishments: the discovery of the concept of the atom to explain the composition of all matter. F This search had its earliest contribution from the ancient Greek philosophers, who suggested air, water, fire, and earth as matter’s fundamental building blocks. It culminated with the A development of the atomic theory and the discovery of matter’s simplest identity, the element. N An element is the simplest substance known and provides the building block from which Y all matter is composed. At present, 118 elements have been identified (see Table 9–1); of these, 89 occur naturally on the earth, and the remainder have been created in the laboratory. In Figure 9–1, all of the elements are listed by name and symbol in a form that has become known 1 as the periodic table. This table is most useful to chemists because it systematically arranges elements with similar chemical5properties in the same vertical row or group. For convenience, chemists have chosen letter symbols to represent the elements. Many of 6 these symbols come from the first letter of the element’s English name—for example, carbon (C), hydrogen (H), and oxygen (O).8Others are two-letter abbreviations of the English name—for example, calcium (Ca) and zinc (Zn). Some symbols are derived from the first letters of Latin or T Greek names. Thus, the symbol for silver, Ag, comes from the Latin name argentum; copper, Cu, S He, from the Greek name helios. from the Latin cuprum; and helium, The smallest particle of an element that can exist and still retain its identity as that element is the atom. When we write the symbol C we mean one atom of carbon; the chemical symbol for carbon dioxide, CO2, signifies one atom of carbon combined with two atoms of oxygen. When two or more elements are combined to form a substance, as with carbon dioxide, a new substance is created, different in its physical and chemical properties from its elemental components. This new material is called a compound. Compounds contain at least two elements. Considering that there are 89 natural elements, it is easy to imagine the large number of possible elemental combinations that may form compounds. Not surprisingly, more than 16 million known compounds have already been identified. MATTER, LIGHT, AND GLASS EXAMINATION 205 TABLE 9–1 List of Elements with Their Symbols and Atomic Masses ISBN: 978-1-323-16745-8 Element Actinum Aluminum Americium Antimony Argon Arsenic Astatine Barium Berkelium Beryllium Bismuth Bohrium Boron Bromine Cadmium Calcium Californium Carbon Cerium Cesium Chlorine Chromium Cobalt Copernicium Copper Curium Darmstadtium Dubnium Dysprosium Einsteinium Erbium Europium Fermium Flerovium Fluorine Francium Gadolinium Gallium Germanium Gold Hafnium Hassium Helium Holmium Hydrogen Indium Iodine Iridium Iron Krypton Lanthanum Lawrencium Symbol Ac Al Am Sb Ar As At Ba Bk Be Bi Bh B Br Cd Ca Cf C Ce Cs Cl Cr Co Cn Cu Cm Ds Db Dy Es Er Eu Fm FL F Fr Gd Ga Ge Au Hf Hs He Ho H In I Ir Fe Kr La Lr Atomic Massa (amu) (227) 26.9815 (243) 121.75 39.948 74.9216 (210) 137.34 (247) 9.01218 208.9806 (270) 10.81 79.904 112.40 40.08 (251) 12.011 140.12 132.9055 35.453 51.996 58.9332 (285) 63.546 (247) (81) (268) 162.50 (254) 167.26 151.96 (253) (289) 18.998 (223) 157.25 69.72 72.59 196.9665 178.49 (277) 4.00260 164.9303 1.0080 114.82 126.9045 192.22 55.847 83.80 138.9055 (262) Element L I D D E L L , T I F F A N Y 1 5 6 8 T S Lead Lithium Livermorium Lutetium Magnesium Manganese Meitnerium Mendelevium Mercury Molybdenum Neodymium Neon Neptunium Nickel Niobium Nitrogen Nobelium Osmium Oxygen Palladium Phosphorus Platinum Plutonium Polonium Potassium Praseodymium Promethium Protactinium Radium Radon Rhenium Rhodium Roentgenium Rubidium Ruthenium Rutherfordium Samarium Scandium Seaborgium Selenium Silicon Silver Sodium Strontium Sulfur Tantalum Technetium Tellurium Terbium Thallium Thorium Thulium Symbol Pb Li Lv Lu Mg Mn Mt Md Hg Mo Nd Ne Np Ni Nb N No Os O Pd P Pt Pu Po K Pr Pm Pa Ra Rn Re Rh Rg Rb Ru Rf Sm Sc Sg Se Si Ag Na Sr S Ta Tc Te Tb Tl Th Tm Atomic Massa (amu) 207.2 6.941 (293) 174.97 24.305 54.9380 (278) (256) 200.59 95.94 144.24 20.179 237.0482 58.71 92.9064 14.0067 (254) 190.2 15.9994 106.4 30.9738 195.09 (244) (209) 39.102 140.9077 (145) 231.0359 226.0254 (222) 186.2 102.9055 (280) 85.4678 101.07 (265) 105.4 44.9559 (271) 78.96 28.086 107.868 22.9898 87.62 32.06 180.9479 98.9062 127.60 158.9254 204.37 232.0381 168.9342 (continued) Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 206 CHAPTER 9 TABLE 9–1 List of Elements with Their Symbols and Atomic Masses (continued) Element Tin Titanium Tungsten Ununoctium Ununpentium Ununseptium Ununtrium Atomic Massa (amu) Symbol Sn Ti W Uuo Uup Uus Uut 118.69 47.90 183.85 (294) (288) (?) (284) Element Symbol Uranium Vanadium Xenon Ytterbium Yttrium Zinc Zirconium U V Xe Yb Y Zn Zr Atomic Massa (amu) 238.029 50.9414 131.3 173.04 88.9059 65.57 91.22 Based on the assigned relative atomic mass of C 5 exactly 12; parentheses denote the mass number of the isotope with the longest half-life. a Group Period IA IIA IIIB IVB VB L I D VIB VIIB D E L L , VIII IB IIB IIIA IVA VA VIA VIIA O 2 He 1 1 H 2 3 Li 4 Be 3 11 Na 12 Mg 4 19 K 20 Ca 21 Sc 22 Ti 23 V 24 25 CrT Mn 26 Fe 27 Co 28 Ni 29 Cu 5 37 Rb 38 Sr 39 Y 40 Zr 41 Nb 42I Mo 43 Tc 44 Ru 45 Rh 46 Pd 6 55 Cs 56 Ba 57 72 La a Hf 73 Ta 74 75 F W Re 76 Os 77 Ir 78 Pt 7 87 Fr 88 Ra 89 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 Ac b Rf Db SgN Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo F 5 B 6 C 7 N 8 O 9 F 10 Ne 13 Al 14 Si 15 P 16 S 17 Cl 18 Ar 30 Zn 31 Ga 32 Ge 33 As 34 Se 35 Br 36 Kr 47 Ag 48 Cd 49 In 50 Sn 51 Sb 52 Te 53 I 54 Xe 79 Au 80 Hg 81 Tl 82 Pb 83 Bi 84 Po 85 At 86 Rn A Y aLanthanide series bActinide series 69 Tm 70 Yb 71 Lu 58 Ce 59 Pr 60 Nd 61 Pm 62 Sm 63 Eu 64 Gd 65 Tb 66 Dy 67 Ho 68 Er 90 Th 91 Pa 921 93 U5 Np 94 Pu 95 Am 96 Cm 97 Bk 98 Cf 99 Es 100 101 102 103 Fm Md No Lr 6 8 T Just as the atom is the basic S particle of an element, the molecule is the smallest unit of a FIGURE 9–1 The periodic table. compound. Thus, a molecule of carbon dioxide is represented by the symbol CO2, and a molecule of table salt is symbolized by NaCl, representing the combination of one atom of the element sodium (Na) with one atom of the element chlorine (Cl). As we look around us and view the materials that make up the earth, it becomes an awesome task even to attempt to estimate the number of different kinds of matter that exist. A much more logical approach is to classify matter according to the physical form it takes. These forms are called Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 States of Matter MATTER, LIGHT, AND GLASS EXAMINATION 207 physical states. There are three such states: solid, liquid, and gas (vapor). A solid is rigid and therefore has a definite shape and volume. A liquid also occupies a specific volume, but its fluidity causes it to take the shape of the container in which it is residing. A gas has neither a definite shape nor volume, and it will completely fill any container into which it is placed. physical state CHANGES OF STATE Substances can change from one state to another. For example, as water A state of matter in which the molecules are held closely together in a rigid state. is heated, it is converted from a liquid form into a vapor. At a high enough temperature (100°C), water boils and rapidly changes into steam. Similarly, at 0°C, water solidifies or freezes into ice. Under certain conditions, some solids can be converted directly into a gaseous state. For instance, a piece of dry ice (solid carbon dioxide) left standing at room temperature quickly forms carbon dioxide vapor and disappears. This change of state from a solid to a gas is called sublimation. In each of these examples, no new chemical species are formed; matter is simply being changed from one physical state to another. Water, whether in the form of liquid, ice, or steam, remains chemically H2O. Simply, what has been altered are the attractive forces between the water molecules. In a solid, these forces are very strong, and theLmolecules are held closely together in a rigid state. In a liquid, the attractive forces are not as Istrong, and the molecules have more mobility. Finally, in the vapor state, appreciable attractive forces no longer exist among the D molecules; thus, they may move in any direction at will. D the solid, liquid, or gaseous states, hoping to create new and E useful products. Our everyday observations should make it apparent that not all attempts at mixing matter can be productive. For instance, oil spills demonstrate that oil and water do not mix.LWhenever substances can be distinguished by a visible boundary, different phases are saidLto exist. Thus, oil floating on water is an example of a two-phase system. The oil and water each constitute a separate liquid phase, clearly distinct from each other. Similarly, when sugar is ,first added to water, it does not PHASES Chemists are forever combining different substances, no matter whether they are in dissolve, and two distinctly different phases exist: the solid sugar and the liquid water. However, after stirring, all the sugar dissolves, leaving just one liquid phase. T Physical Properties of Matter I All materials possess a range of physical properties whose measurement is critical to the work of F the forensic scientist. Several of the most important of these for the forensic characterization of F glass is density and refractive index. Which physical and chemical properties the forensic scientist ultimately chooses to observe A and measure depends on the type of material that is being examined. Logic requires, however, N to a standard system of meathat if the property can be assigned a numerical value, it must relate surement accepted throughout the scientific community. Y A condition or stage in the form of matter; a solid, liquid, or gas. solid liquid A state of matter in which molecules are in contact with one another but are not rigidly held in place. gas (vapor) A state of matter in which the attractive forces between molecules are small enough to permit them to move with complete freedom. sublimation A physical change from the solid state directly into the gaseous state. phase A uniform body of matter; different phases are separated by definite visible boundaries. Basic Units of Measurement ISBN: 978-1-323-16745-8 The metric system has basic units of measurement for length, mass, 1 and volume: the meter, gram, and liter, respectively. These three basic units can be converted into subunits that are decimal multiples of the basic unit by simply attaching a prefix to the unit5name. The following are common prefixes and their equivalent decimal value: 6 8 T S Prefix Equivalent Value decicentimillimicronanokilomega- 1/10 or 0.1 1/100 or 0.01 1/1000 or 0.001 1/1,000,000 or 0.000001 1/1,000,000,000 or 0.000000001 1,000 1,000,000 Hence, 1/10 or 0.1 gram (g) is the same as a decigram (dg), 1/100 or 0.01 meter is equal to a centimeter (cm), and 1/1,000 liter is a milliliter (mL). A metric conversion is carried out simply Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 208 CHAPTER 9 inside the science The Metric System Although scientists, including forensic scientists, throughout the world have been using the metric system of measurement for more than a century, the United States still uses the cumbersome “English system” to express length in inches, feet, or yards; weight in ounces or pounds; and volume in pints or quarts. The inherent difficulty of this system is that no simple numerical relationship exists between the various units of measurement. For example, to convert inches to feet one must know that 1 foot equals 12 inches; conversion of ounces to pounds requires the knowledge that 16 ounces equals 1 pound. In 1791, the French Academy of Science devised the simple system of measurement known as the metric system. This system uses a simple decimal relationship so that a unit of length, volume, or mass can be converted into a subunit by simply multiplying or dividing Lby a multiple of 10—for example, 10, 100, or 1,000. Even though the United States has not yet adI opted the metric system, its system of currency is Ddecimal and, hence, is analogous to the metric system. The basic unit of currency is the dollar. A dollar Dis divided into 10 equal units called dimes, and each Edime is further divided into 10 equal units of cents. L L , T I 10 cm F F A 10 cm N 1,000 cm3 1 liter (1 L) = Y 1,000 mL 10 cm 1 cm 1 cm 1 cm 1 cm3 = 1mL Volume equivalencies in the metric system. 1 5 6 8 T measurement; 2.54 centimeters 5 1 inch. Comparison of the metric and English systems of length S Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 by moving the decimal point to the right or left and inserting the proper prefix to show the direction and number of places that the decimal point has been moved. For example, if the weight of a powder is 0.0165 gram, it may be more convenient to multiply this value by 100 and express it as 1.65 centigrams or by 1,000 to show it as its equivalent value of 16.5 milligrams. Similarly, an object that weighs 264,450 grams may be expressed as 264.45 kilograms simply by dividing it by 1,000. It is important to remember that in any of these conversions, the value of the measurement MATTER, LIGHT, AND GLASS EXAMINATION 209 has not changed; 0.0165 gram is still equivalent to 1.65 centigrams, just as one dollar is still equal to 100 cents. We have simply adjusted the position of the decimal and shown the extent of the adjustment with a prefix. One interesting aspect of the metric system is that volume can be defined in terms of length. A liter by definition is the volume of a cube with sides of length 10 centimeters. One liter is therefore equivalent to a volume of 10 cm 3 10 cm 3 10 cm, or 1,000 cubic centimeters (cc). Thus, 1/1,000 liter or 1 milliliter (mL) is equal to 1 cubic centimeter (cc). Scientists commonly use the subunits mL and cc interchangeably to express volume. Metric Conversion At times, it may be necessary to convert units from the metric system into the English system, or vice versa. To accomplish this, we must consult references that list English units and their metric equivalents. Some of the more useful equivalents follow: L I D D The general mathematical procedures for converting from one E system to another can be illustrated by converting 12 inches into centimeters. To change inches into centimeters, we need to L 12 inches by 2.54 centimeters know that there are 2.54 centimeters per inch. Hence, if we multiply per inch (12 in. 3 2.54 cm/in.), the unit of inches will cancel out,Lleaving the product 30.48 cm. Similarly, applying the conversion of grams to pounds, 227 grams is equivalent to 227 g 3 , 1 lb/453.6 g or 0.5 lb. 1 inch 5 2.54 centimeters 1 meter 5 39.37 inches 1 pound 5 453.6 grams 1 liter 5 1.06 quarts 1 kilogram 5 2.2 pounds Density T An important physical property of matter with respect to the analysis of certain kinds of physical evidence is density. Density is defined as mass per unit volumeI [see Equation (9–1)]. F (9–1) F A Density is an intensive property of matter—that is, it is the same regardless of the size Nand can be used as an aid in of a substance; thus, it is a characteristic property of a substance identification. Solids tend to be more dense than liquids, and liquids Y more dense than gases. The ISBN: 978-1-323-16745-8 mass Density = volume densities of some common substances are shown in Table 9–2. A simple procedure for determining the density of a solid is illustrated in Figure 9–2. First, the solid is weighed on a balance against known standard gram1 weights to determine its mass. The solid’s volume is then determined from the volume of water it displaces. This is easily mea5 the object, and measuring sured by filling a cylinder with a known volume of water (V1), adding the new water level (V2). The difference V2—V1 in milliliters is equal 6 to the volume of the solid. Density can now be calculated from Equation (9–1) in grams per milliliter. 8 The volumes of gases and liquids vary considerably with temperature; hence, when determining density, it is important to control and record the temperature T at which the measurements are made. For example, 1 gram of water occupies a volume of 1 milliliter at 4°C and thus has a density of 1.0 g/mL. However, as the temperature of water S increases, its volume expands. Therefore, at 20°C (room temperature) 1 gram of water occupies a volume of 1.002 mL and has a density of 0.998 g/mL. The observation that a solid object either sinks, floats, or remains suspended when immersed in a liquid can be accounted for by the property of density. For instance, if the density of a solid is greater than that of the liquid in which it is immersed, the object sinks; if the solid’s density is less than that of the liquid, it floats; and when the solid and liquid have equal densities, the solid remains suspended in the liquid. As we will shortly see, these observations provide a convenient technique for comparing the densities of solid objects. density A physical property of matter that is equivalent to the mass per unit volume of a substance. intensive property A property that is not dependent on the size of an object. Fahrenheit scale The temperature scale using the melting point of ice as 32° and the boiling point of water as 212°, with 180 equal divisions or degrees between. Celsius scale The temperature scale using the melting point of ice as 0° and the boiling point of water as 100°, with 100 equal divisions or degrees between. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 210 CHAPTER 9 inside the science Temperature Determining the physical properties of any material often requires measuring its temperature. For instance, the temperatures at which a substance melts or boils are readily determinable characteristics that will help identify it. Temperature is a measure of heat intensity, or the amount of heat in a substance. Temperature is usually measured by causing a thermometer to come into contact with a substance. The familiar mercury-in-glass thermometer functions because mercury expands more than glass when heated and contracts more than glass when cooled. Thus, the length of the mercury column in the glass tube provides a measure of the surrounding environment’s temperature. The construction of a temperature scale requires two reference points and a choice of units. The reference points most conveniently chosen are the freezing point and boiling point of water. The two most common temperature scales used are the Fahrenheit and Celsius (formerly called centigrade) scales. The Fahrenheit scale is based on assigning a value of 32°F to the freezing point of water and a value of 212°F to its boiling point. The difference between the two points is evenly divided into 180 units. Thus, a degree Fahrenheit is 1/180 of the temperature change between the freezing point and boiling point of water. The Celsius scale is derived by assigning the freezing point of water a value of 0°C and its boiling point a value of 100°C. A degree Celsius is thus 1/100 of the temperature change between the two reference points. Scientists in most countries use the Celsius scale to inside the science Weight and Mass 100º L I D D E L L , T I F F A N Y 1 5 6 8 T S 90º 220º 212º 200º 80º 180º 70º 160º 60º 140º 50º 120º 40º 100º 30º 80º Normal room temperature 40º 32º 20º Freezing point of water 10º - 10º - 20º - 30º Celsius Normal body temperature 60º 20º 0º Boiling point of water 0º - 20º Fahrenheit Comparison of the Celsius and Fahrenheit temperature scales. Mass differs from weight because it refers to the amount of matter an object contains and is independent of its location on earth or any other place in the universe. The mathematical relationship between weight (w) and mass (m) is shown in Equation (9–2), where g is the acceleration imparted to a body by the force of gravity. W ⫽ mg (9–2) Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 The force with which gravity attracts a body is called weight. If your weight is 180 pounds, this means that the earth’s gravity is pulling you down with a force of 180 pounds; on the moon, where the force of gravity is one-sixth that of the earth, your weight would be 30 pounds. measure temperature. A comparison of the two scales is shown below. Unknown masses Known masses L I D D The measurement of mass. E L L , Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com The weight of a body is directly proportional to its mass; hence, a large mass weighs more than a small mass. In the metric system, the mass of an object is always specified, rather than its weight. The basic unit of mass is the gram. An object that has a mass of 40 grams on earth will have a mass of 40 grams anywhere else in the universe. Normally, however, the terms mass and weight are used interchangeably, and we often speak of the weight of an object when we really mean its mass. The mass of an object is determined by comparing it against the known mass of standard objects. The comparison is confusingly called weighing, and the standard objects are called weights (masses would be a more correct term). The comparison is performed on a balance. The simplest type of balance for weighing is the equal-arm balance shown in the figure. The object to be weighed is placed on the left pan, and the standard weights are placed on the right pan; when the pointer between the two pans is at the center mark, the total mass on the right pan is equal to the mass of the object on the left pan. The modern laboratory has progressed beyond the simple equal-arm balance, and either the top-loading balance or the single-pan analytical balance as shown in the figures is now likely to be used. The choice depends on the accuracy required and the amount of material being weighed. Each works on the same counterbalancing principle as the simple equal-arm balance. Earlier versions of the single-pan balance had a second pan, the one on which the standard weights were placed. This pan was hidden from view within the balance’s housing. Once the object whose weight was to be determined was placed on the visible pan, the operator selected the proper standard weights (also contained within the housing) by manually turning a set of knobs located on the front side of the balance. At the point of balance, the weights selected were automatically recorded on optical readout scales. Modern single-pan balances may employ an electromagnetic field to generate a current to balance the force pressing down on the pan from the sample being weighed. When the scale is properly calibrated, the amount of current needed to keep the pan balanced is used to determine the weight of the sample. The strength of the current is converted to a digitized signal for a readout. Another approach is to employ a bridge circuit incorporating a strain gauge resistor that changes in response to the force applied to it. The top-loading balance can accurately weigh an object to the nearest 1 milligram or 0.001 gram; the analytical balance is even more accurate, weighing to the nearest tenth of a milligram or 0.0001 gram. T I F F (a) A N Y 1 5 6 8 T S 211 Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com ISBN: 978-1-323-16745-8 MATTER, LIGHT, AND GLASS EXAMINATION (b) (a) Top-loading balance. (b) Single-pan analytical balance. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 212 CHAPTER 9 mass A constant property of matter that reflects the amount of material present. weight A property of matter that depends on both the mass of a substance and the effects of gravity on that mass. TABLE 9–2 Densities of Select Materials (at 20°C Unless Otherwise Stated) Substance Density (g/mL) Solids Silver Lead Iron Aluminum Window glass Ice (0°C) 10.5 11.5 7.8 2.7 2.47–2.54 0.92 Liquids Mercury Benzene Ethyl alcohol Gasoline Water at 4°C Water 13.6 0.88 0.79 0.69 1.00 0.998 L I D D Gases E Air (0°C) L Chlorine (0°C) Oxygen (0°C) L Carbon dioxide (0°C) , FIGURE 9–2 A simple procedure for determining the density of a solid is first to measure its mass on a scale and then to measure its volume by noting the volume of water it displaces. 0.0013 0.0032 0.0014 0.0020 T I F F A N Y 1 5 Density 6 ⫽ 8 Density ⫽ T S Density ⫽ Mass = 20 g 70 70 60 60 50 50 40 40 30 30 20 20 10 10 Mass Volume (v2 ⫺ v1) 75g (50ml ⫺ 40ml) 75g 10ml Volume ⫽ 7.5g/ml refraction The bending of a light wave as it passes from one medium to another. Light, as we will learn in the next section, can have the property of a wave. Light waves travel in air at a constant velocity of nearly 300 million meters per second until they penetrate another medium, such as glass or water, at which point they are suddenly slowed, causing the rays to bend. The bending of a light wave because of a change in velocity is called refraction. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 Refractive Index MATTER, LIGHT, AND GLASS EXAMINATION 213 FIGURE 9–3 Light is refracted when it travels obliquely from one medium to another. Apparent position of ball Air Water Ball L I The phenomenon of refraction is apparent when we view an D object that is immersed in a transparent medium; because we are accustomed to thinking that light travels in a straight line, D a ball is observed at the we often forget to take refraction into account. For instance, suppose bottom of a pool of water; the light rays reflected from the ball travel E through the water and into the air to reach the eye. As the rays leave the water and enter the air, their velocity suddenly inL creases, causing them to be refracted. However, because of our assumption that light travels in a straight line, our eyes deceive us and make us think we see an object lying at a higher point than L is actually the case. This phenomenon is illustrated in Figure 9–3. , determines the refractive The ratio of the velocity of light in a vacuum to that in any medium index of that medium and is expressed as follows: Refractive index 5 T velocity of light in vacuum velocity of light in medium I refractive index The ratio of the speed of light in a vacuum to its speed in a given substance. F For example, at 25°C the refractive index of water is 1.333. This means that light travels 1.333 times as fast in a vacuum as it does in water at this temperature. F Like density, the refractive index is an intensive physical property of matter and characterA izes a substance. However, any procedure used to determine a substance’s refractive index must be performed under carefully controlled temperature and lightingNconditions because the refractive index of a substance varies with its temperature and the wavelength of light passing through Y it. Nearly all tabulated refractive indices are determined at a standard wavelength, usually 589.3 nanometers; this is the predominant wavelength emitted by sodium light and is commonly known as the sodium D light. 1 5 similar refractive index, light is not refracted as it passes from the liquid into the solid. For this 6 the solid seems to disappear reason, the eye cannot distinguish the liquid–solid boundary, and from view. This observation, as we will see, offers the forensic8scientist a simple method for comparing the refractive indices of transparent solids. T index value for each waveNormally, we expect a solid or a liquid to exhibit only one refractive length of light; however, many crystalline solids have two refractiveSindices whose values depend in ISBN: 978-1-323-16745-8 COMPARING REFRACTIVE INDICES When a transparent solid is immersed in a liquid with a part on the direction in which the light enters the crystal with respect to the crystal axis. Crystalline solids have definite geometric forms because of the orderly arrangement of the fundamental particle of a solid, the atom. In any type of crystal, the relative locations and distances between its atoms are repetitive throughout the solid. Figure 9–4 shows the crystalline structure of sodium chloride, or ordinary table salt. Sodium chloride is an example of a cubic crystal in which each sodium atom is surrounded by six chloride atoms and each chloride atom by six sodium atoms, except at the crystal surface. Not all solids are crystalline in nature; some, such as glass, have their atoms arranged randomly throughout the solid; these materials are known as amorphous solids. Most crystals, excluding those that have cubic configurations, refract a beam of light into two different light-ray components. This phenomenon, known as double refraction, can be observed by studying the behavior of the crystal calcite. When the calcite is laid on a printed page, crystalline solid A solid in which the constituent atoms have a regular arrangement. atom The smallest unit of an element, which is not divisible by ordinary chemical means; atoms are made up of electrons, protons, and neutrons plus other subatomic particles. amorphous solid A solid in which the constituent atoms or molecules are arranged in random or disordered positions; there is no regular order in amorphous solids. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 214 CHAPTER 9 FIGURE 9–4 Diagram of a sodium chloride crystal. Sodium is represented by the darker spheres, chlorine by the lighter spheres. L I D D WhiteE light L L , Slit Prism Screen Red Violet Red Orange Yellow Green Blue Violet FIGURE 9–5 T Representation of the dispersion of light by a glass prism. birefringence A difference in the two indices of refraction exhibited by most crystalline materials. dispersion The separation of light into its component wavelengths. Colored light ranging from red to violet in the electromagnetic spectrum. transform light into the colors of the rainbow. This observation demonstrates that visible “white light” is not homogeneous but is actually composed of many different colors. The process 1 of separating light into its component colors is called dispersion. The ability of a prism to disperse light into its component 5 colors is explained by the property of refraction. Each color component of light, on passing through the glass, is slowed to a speed slightly different from 6 component to bend at a different angle as it emerges from the those of the others, causing each prism. As shown in Figure 9–5,8the component colors of visible light extend from red to violet. Dispersion thus separates light into its component wavelengths and demonstrates that glass has a T slightly different index of refraction for each wavelength of light passing through it. We have already seen thatSwhen white light passes through a glass prism, it is dispersed into a continuous spectrum of colors. This phenomenon demonstrates that white light is not homogeneous but is actually composed of a range of colors that extends from red through violet. Similarly, the observation that a substance has a color is also consistent with this description of white light. For example, when light passes through a red glass, the glass absorbs all the component colors of light except red, which passes through or is transmitted by the glass. Likewise, one can determine the color of an opaque object by observing its ability to absorb some of the component colors of light while reflecting others back to the eye. Color is thus a visual indication that objects absorb certain portions of visible light and transmit or reflect others. Scientists have long recognized this phenomenon and have learned to characterize different chemical substances by the type and quantity of light they absorb. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 visible light I F the observer sees not one but two images of each word covered. The two light rays that give rise F at different angles, and each has a different refractive index to the double image are refracted value. The indices of refractionA for calcite are 1.486 and 1.658, and subtracting the two values yields a difference of 0.172; this difference is known as birefringence. Thus, the optical properties of crystals provide points ofNidentification that help characterize them. Y held a glass prism up toward the sunlight and watched it DISPERSION Many of us have MATTER, LIGHT, AND GLASS EXAMINATION 215 λ L I D λ D FIGURE 9–6 E The frequency of the lower wave is twice that of the upper wave. L L Theory of Light To understand why materials absorb light, one must first comprehend , the nature of light. Two simple models explain light’s behavior. The first model describes light as a continuous wave; the second depicts it as a stream of discrete energy particles. Together, these two very different descriptions explain all of the observed properties of light, but by T itself, no one model can explain all the facets of the behavior of light. I F continuous wave, as shown in Figure 9–6. Several terms are used to describe such a wave. The distance between two consecutive crests (or one trough toFthe next trough) is called the wavelength; the Greek letter lambda (λ) is used as its symbol, and the unit of nanometers is A frequently used to express its value. The number of crests (or troughs) passing any one given N point in a unit of time is defined as the frequency of the wave. Frequency is normally designated by the letter f and is expressed in cycles per second (cps). The speed of light in a vacuum is a Y universal constant at 300 million meters per second and is designated by the symbol c. Frequency LIGHT AS A WAVE The wave concept depicts light as having an up-and-down motion of a and wavelength are inversely proportional to one another, as shown by the relationship expressed in Equation (9–3): 1 5 (9–3) 6 THE ELECTROMAGNETIC SPECTRUM Actually, visible light is 8 only a small part of a large family of radiation waves known as the electromagnetic spectrum. All electromagnetic waves T travel at the speed of light (c) and are distinguishable from one another only by their different wavelengths or frequencies. Figure 9–7 illustrates the various types S of electromagnetic waves in ISBN: 978-1-323-16745-8 F5 wavelength The distance between crests of adjacent waves. frequency The number of waves that pass a given point per second. c λ order of decreasing frequency.) Hence, the only property that distinguishes X-rays from radio waves is the different frequencies the two types of waves possess. Similarly, the range of colors that make up the visible spectrum can be correlated with frequency. For instance, the lowest frequencies of visible light are red; waves with a lower frequency fall into the invisible infrared (IR) region. The highest frequencies of visible light are violet; waves with a higher frequency extend into the invisible ultraviolet (UV) region. No definite boundaries exist between any colors or regions of the electromagnetic spectrum; instead, each region is composed of a continuous range of frequencies, each blending into the other. Ordinarily, light in any region of the electromagnetic spectrum is a collection of waves possessing a range of wavelengths. Under normal circumstances, this light comprises waves that are electromagnetic spectrum The entire range of radiation energy from the most energetic cosmic rays to the least energetic radio waves. X-ray A high-energy, short-wavelength form of electromagnetic radiation. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 216 CHAPTER 9 FIGURE 9–7 The electromagnetic spectrum. Energy increases Short wavelength Gamma rays Long wavelength X rays Ultraviolet Infrared Microwaves High frequency Radio waves Low frequency Visible light FIGURE 9–8 Coherent and incoherent radiation. L I D D E L L , Coherent radiation T I F F A N Y Incoherent radiation 1 laser An acronym for light amplification by stimulated emission of radiation; light that has all its waves pulsating in unison. photon T as electromagnetic radiation is moving through space, its As long behavior can be described as that S of a continuous wave; however, once radiation is absorbed by a substance, the model of light as a stream of discrete particles must be invoked to best describe its behavior. Here, light is depicted as consisting of energy particles that are known as photons. Each photon has a definite amount of energy associated with its behavior. This energy is related to the frequency of light, as shown by Equation (9–4): LIGHT AS A PARTICLE E 5 hf (9–4) where E specifies the energy of the photon, f is the frequency of radiation, and h is a universal constant called Planck’s constant. As shown by Equation (9–4), the energy of a photon is directly proportional to its frequency. Therefore, the photons of ultraviolet light will be more energetic than the photons of visible or infrared light, and exposure to the more energetic photons of X-rays presents more danger to human health than exposure to the photons of radio waves. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 A small packet of electromagnetic radiation energy; each photon contains a unit of energy equal to the product of Planck’s constant and the frequency of radiation: E 5 hf. all out of step with each other (incoherent light). However, scientists can now produce a beam of 5 light that has all of its waves pulsating in unison (see Figure 9–8). This is called coherent light or a laser (light amplification by the stimulated emission of radiation) beam. Light in this form 6 is very intense and can be focused on a very small area. Laser beams can be focused to pinpoints that are so intense that they can8 zap microscopic holes in a diamond. MATTER, LIGHT, AND GLASS EXAMINATION 217 Now that we have investigated various physical properties of objects, we are ready to apply such properties to the forensic characterization of glass. Forensic Analysis of Glass Glass that is broken and shattered into fragments and minute particles during the commission of a crime can be used to place a suspect at the crime scene. For example, chips of broken glass from a window may lodge in a suspect’s shoes or garments during a burglary, or particles of headlight glass found at the scene of a hit-and-run accident may offer clues that can confirm the identity of a suspect vehicle. All of these possibilities require the comparison of glass fragments found on the suspect, whether a person or vehicle, with the shattered glass remaining at the crime scene. Composition of Glass L Glass is a hard, brittle, amorphous substance composed of sand (silicon oxides) mixed with variI at high temperatures, and ous metal oxides. When sand is mixed with other metal oxides, melted then cooled to a rigid condition without crystallization, the product D is glass. Soda (sodium carbonate) is normally added to the sand to lower its melting point and make it easier to work with. Another necessary ingredient is lime (calcium oxide), needed toDprevent the “soda-lime” glass from dissolving in water. The forensic scientist is often asked to E analyze soda-lime glass, which is used for manufacturing most window and bottle glass. Often the molten glass is cooled on a L typically used for windows. bed of molten tin. This manufacturing process produces flat glass This type of glass is called float glass. L The common metal oxides found in soda-lime glass are sodium, calcium, magnesium, and , by substituting in whole or aluminum. In addition, a wide variety of special glasses can be made in part other metal oxides for the silica, sodium, and calcium oxides. For example, automobile headlights and heat-resistant glass, such as Pyrex, are manufactured by adding boron oxide to the oxide mix. These glasses are therefore known as borosilicates. T Another type of glass that the reader may be familiar with isI tempered glass. This glass is made stronger than ordinary window glass by introducing stress through rapid heating and cooling of the glass surfaces. When tempered glass breaks, it does notFshatter but rather fragments or “dices” into small squares with little splintering (see Figure 9–9).FBecause of this safety feature, tempered glass is used in the side and rear windows of automobiles made in the United States, as A of all cars manufactured well as in the windshields of some foreign-made cars. The windshields in the United States are constructed from laminated glass. This N glass derives its strength by sandwiching one layer of plastic between two pieces of ordinary window glass. Y ISBN: 978-1-323-16745-8 Comparing Glass Fragments tempered glass Glass that is strengthened by introducing stress through rapid heating and cooling of the glass surfaces. laminated glass Two sheets of ordinary glass bonded together with a layer of plastic. 1 measuring the properties that For the forensic scientist, comparing glass consists of finding and will associate one glass fragment with another while minimizing or 5 eliminating the possible existence of other sources. Considering the prevalence of glass in our society, it is easy to appreciate 6 its greatest evidential value the magnitude of this analytical problem. Obviously, glass possesses when it can be individualized to one source. Such a determination, 8 however, can be made only when the suspect and crime-scene fragments are assembled and physically fitted together. ComT glass as well as matching parisons of this type require piecing together irregular edges of broken all irregularities and striations on the broken surfaces (see FigureS 9–10). The possibility that two pieces of glass originating from different sources will fit together exactly is so unlikely as to exclude all other sources from practical consideration. Unfortunately, most glass evidence is either too fragmentary or too minute to permit a comparison of this type. In such instances, the search for individual properties has proven fruitless. For example, the general chemical composition of various window glasses within the capability of current analytical methods has so far been found relatively uniform among various manufacturers and thus offers no basis for individualization. However, as discussed in Chapter 13, trace elements present in glass have been shown to be useful for narrowing the origin of a glass specimen. The physical properties of density and refractive index are most widely used for characterizing glass particles. However, these properties are class characteristics, which cannot provide the sole criteria for individualizing glass to a common source. They do, however, give Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. L I D D E L L , FIGURE 9–9 When tempered glass breaks, it usually holds together without splintering. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com CHAPTER 9 Thinkstock 218 FIGURE 9–10 Match of broken glass. Note the physical fit of the edges. T the analyst sufficient data to evaluate the significance of a glass comparison, and the absence of I comparable density and refractive index values will certainly exclude glass fragments that originate from different sources. F F Measuring and Comparing Density Recall that a solid particle will A either float, sink, or remain suspended in a liquid, depending on its density relative to the liquid.N This knowledge gives the criminalist a rather precise and rapid method for comparing densities of glass. In a method known as flotation, a standard/reference Y a mixture of bromoform and bromobenzene may be used. glass particle is immersed in a liquid; The composition of the liquid is carefully adjusted by the addition of small amounts of bromoform or bromobenzene until the glass chip remains suspended in the liquid medium. At this point, the standard/reference glass and1liquid each have the same density. Glass chips of approximately the same size and shape as the 5 standard/reference are now added to the liquid for comparison. If both the unknown and the standard/reference particles remain suspended in the liquid, their 6and to that of the liquid.1 Particles of different densities either densities are equal to each other sink or float, depending on whether 8 they are more or less dense than the liquid. The density of a single sheet of window glass is not completely homogeneous throughout. It T by as much as 0.0003 g/mL. Therefore, in order to distinguish has a range of values that can differ between the normal internal density S variations of a single sheet of glass and those of glasses of different origins, it is advisable to let the comparative density approach but not exceed a sensitivity value of 0.0003 g/mL. The flotation method meets this requirement and can adequately distinguish glass particles that differ in density by 0.001 g/mL. Once glass has been distinguished by a density determination, different origins are immediately concluded. Comparable density results, however, require the added comparison of refractive 1 As an added step, the analyst can determine the exact numerical density value of the particles of glass by transferring the liquid to a density meter, which will electrically measure and calculate the liquid’s density. See A. P. Beveridge and C. Semen, “Glass Density Measurement Using a Calculating Digital Density Meter,” Canadian Society of Forensic Science Journal 12 (1979): 113. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 Determining and Comparing Refractive Index MATTER, LIGHT, AND GLASS EXAMINATION 219 Courtesy of Chris Palenik of Microtrace LLC, Elgin, IL FIGURE 9–11 Hot-stage microscope. L I D D E indices. This determination is best accomplished by the immersion L method. For this, glass particles are immersed in a liquid medium whose refractive index is adjusted until it equals that of the Lnotes the disappearance of the glass particles. At this point, known as the match point, the observer Becke line and minimum contrast between the glass and liquid medium. The Becke line is a bright , halo that is observed near the border of a particle that is immersed in a liquid of a different refractive index. This halo disappears when the medium and fragment have similar refractive indices. The refractive index of an immersion fluid is best adjusted by T changing the temperature of the liquid. Temperature control is, of course, critical to the success of the procedure. One apI known as a hot stage. The proach to this procedure is to heat the liquid in a special apparatus glass is immersed in a liquid, usually a silicone oil, and heated F at the rate of 0.2°C per minute until the match point is reached. Increasing the temperature of the liquid has a negligible effect F at the rate of approximately on the refractive index of glass, whereas the liquid’s index decreases 0.0004 per degree Celsius. The hot stage, as shown in FigureA 9–11, is designed to be used in conjunction with a microscope, through which the examiner can observe the disappearance of the Becke line on minute glass particles that are illuminatedNwith sodium D light or other wavelengths of light. If all the glass fragments examined have Y similar match points, it can be concluded that they have comparable refractive indices (see Figure 9–12). Furthermore, the examiner can determine the refractive index value of the immersion fluid as it changes with temperature. With this information, the exact numerical value of1the glass refractive index can be calculated at the match point temperature.2 5 of plate glass may not have As with density, glass fragments removed from a single sheet a uniform refractive index value; instead, their values may vary6by as much as 0.0002. Hence, for comparison purposes, the difference in refractive index between a standard/reference and 8 to differentiate between the questioned glass must exceed this value. This allows the examiner normal internal variations present in a sheet of glass and those present T in glasses that originated from completely different sources. Becke line A bright halo that is observed near the border of a particle immersed in a liquid of a different refractive index. S ISBN: 978-1-323-16745-8 Classification of Glass Samples A significant difference in either density or refractive index proves that the glasses examined do not have a common origin. But what if two pieces of glass exhibit comparable densities and comparable refractive indices? How certain can one be that they did, indeed, come from the same source? After all, there are untold millions of windows and other glass objects in this world. To provide a reasonable answer to this question, the FBI Laboratory has collected density and refractive index values from glass submitted to it for examination. What has emerged is a data bank 2 A. R. Cassista and P. M. L. Sandercock, “Precision of Glass Refractive Index Measurements: Temperature Variation and Double Variation Methods, and the Value of Dispersion,” Canadian Society of Forensic Science Journal 27 (1994): 203. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 220 CHAPTER 9 FIGURE 9–12 Determination of the refractive index of glass. (a) Glass particles are immersed in a liquid of a much higher refractive index at a temperature of 20°C. (b) At 68°C the liquid still has a higher refractive index than the glass. (c) The refractive index of the liquid is closest to that of the glass at 100°C, as shown by the disappearance of the glass and the Becke lines. (d) At the higher temperature of 160°C, the liquid has a much lower index than the glass, resulting in significant edge contrast. The reference glass fragments shown here has a refractive index of 1.529. (a) (b) L I D D E L L , (c) (d) T I correlating these values to their frequency of occurrence in the glass population of the United F to all forensic laboratories in the United States. States. This collection is available Once a criminalist has completed a comparison of glass fragments, he or she can correlate F their density and refractive index values to their frequency of occurrence and assess probability A same source. Figure 9–13 shows the distribution of refractive that the fragments came from the index values (measured with sodium N D light) for approximately two thousand glasses analyzed by the FBI. The wide distribution of values clearly demonstrates that the refractive index is a Y and is thus useful for defining its frequency of occurrence and highly distinctive property of glass 3 G. Edmondstone, “The Identification of Heat Strengthened Glass in Windshields,” Canadian Society of Forensic Science Journal 30 (1997): 181. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 hence its evidential value. For example, a glass fragment with a refractive index value of 1.5290 is found in approximately only 1 out of 2,000 specimens, whereas glass with a value of 1.5180 1 out of 2,000. occurs approximately in 22 glasses Although refractive index and 5 density have been routinely used for the comparison of glass for some time, forensic scientists have long desired to extract additional information from glass frag6 ments that would make their comparison more meaningful. The trace elemental composition of glass held a longtime attraction to forensic scientists for this purpose. However, until recently, the analyti8 cal instrumentation sensitive enough to develop a trace elemental profile from a glass fragment was T This handicap has been overcome with the introduction of a too costly for most crime laboratories. technique that aims a high-energy Slaser pulse to vaporize a microscopic amount of glass, raising its temperature by thousands of degrees. As a result, the elements present in the glass are induced to emit light whose wavelengths correspond to the identity of the elements present (see Figure 9–14). The distinction between tempered and nontempered glass particles can be made by slowly heating and then cooling the glass (a process known as annealing). The change in the refractive index value for tempered glass upon annealing is significantly greater when compared to nontempered glass and thus serves as a point of distinction.3 MATTER, LIGHT, AND GLASS EXAMINATION 221 Inside the Science GRIM 3 L I D D E L L , Photo courtesy of Foster & Freeman An automated approach for measuring the refractive index of glass fragments by temperature control using the immersion method with a hot stage is with the instrument known as GRIM 3 (glass refractive index measurement) (see the figure). The GRIM 3 is a personal computer/video system designed to automate the measurements of the match temperature and refractive index for glass fragments. This instrument uses a video camera to view the glass fragments as they are being heated. As the immersion oil is heated or cooled, the contrast of the video image is measured continually until a minimum, the match point, is detected (see figure). The match point temperature is then converted to a refractive index using stored calibration data. T I F F A N Y ISBN: 978-1-323-16745-8 1 5 6 8 T S Courtesy Foster & Freeman Limited, Worcestershire, U.K., www.fosterfreeman.co.uk ASKED JANE FOR UPDATED CREDIT LINE An automated system for glass fragment identification. GRIM 3 identifies the refraction match point by monitoring a video image of four different areas of the glass fragment immersed in an oil. As the immersion oil is heated or cooled, the contrast of the image is measured continuously until a minimum, the match point, is detected. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 222 CHAPTER 9 120 100 60 40 20 L I D D E L L , 1.5200 0 1.5100 1.5120 1.5140 1.5160 1.5180 1.5220 1.5240 1.5260 1.5280 1.5300 1.5110 1.5130 1.5150 1.5170 1.5190 1.5210 1.5230 1.5250 1.5270 1.5290 Refractive index Federal Bureau of Investigation Number of specimens 80 T FIGURE 9–13 Frequency of occurrence of refractive index values (measured with sodium D light) for approximately two I thousand flat glass specimens received by the FBI Laboratory. 1 5 6 8 T S Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 Photo courtesy of Foster & Freeman FIGURE 9–14 The elemental profile of a glass fragment is obtained by aiming a high-energy laser beam at a glass particle, inducing the emission of light wavelengths corresponding to the identity of the elements present in the glass. F F A N Y MATTER, LIGHT, AND GLASS EXAMINATION 223 Glass Fractures Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com ISBN: 978-1-323-16745-8 Glass bends in response to any force exerted on any one of its surfaces; when the limit of its elasticity is reached, the glass fractures. Frequently, fractured window glass reveals information that can be related to the force and direction of an impact; such knowledge may be useful for reconstructing events at a crime-scene investigation. The penetration of ordinary window glass by a projectile, whether a bullet or a stone, produces a familiar fracture pattern in which cracks both radiate outward and encircle the hole, as shown in Figure 9–15. The radiating lines are appropriately known as radial fractures, and the circular lines are termed concentric fractures. Often it is difficult to determine just from the size and shape of a hole in glass whether it was made by a bullet or by some other projectile. For instance, a small stone thrown at a comparatively high speed against a pane of glass often produces a hole similar to that produced by a bullet. On the other hand, a large stone can completely shatter a pane of glass in a manner closely L resembling the result of a close-range shot. However, in the latter instance, the presence of gunI caused by a firearm. powder deposits on the shattered glass fragments points to damage When it penetrates glass, a high-velocity projectile such asDa bullet often leaves a round, crater-shaped hole surrounded by a nearly symmetrical pattern of radial and concentric cracks. The D examining it is an important hole is inevitably wider on the exit side (see Figure 9–16), and hence step in determining the direction of impact. However, as the velocity E of the penetrating projectile decreases, the irregularity of the shape of the hole and of its surrounding cracks increases, so that at some point the hole shape will not help determine the direction of L impact. At this time, examining the radial and concentric fracture lines may help determine the direction L of impact. When a force pushes on one side of a pane of glass, the elasticity of the glass permits it to , exceeded, the glass begins to bend in the direction of the force applied. Once the elastic limit is crack. As shown in Figure 9–17, the first fractures form on the surface opposite that of the penetrating force and develop into radial lines. The continued motion of the force places tension on T cracks. An examination of the front surface of the glass, resulting in the formation of concentric the edges of the radial and concentric cracks frequently reveals Istress markings (Wallner lines) whose shape can be related to the side on which the window first cracked. F are perpendicular to one glass Stress marks, shown in Figure 9–18, are shaped like arches that surface and curved nearly parallel to the opposite surface. The importance of stress marks stems F from the observation that the perpendicular edge always faces the surface on which the crack A crack near the point of imoriginated. Thus, in examining the stress marks on the edge of a radial pact, the perpendicular end is always found opposite the side fromNwhich the force of impact was applied. For a concentric fracture, the perpendicular end always faces the surface on which the Y force originated. A convenient way for remembering these observations is the 3R rule—Radial cracks form a Right angle on the Reverse side of the force. These facts enable the examiner to determine the side on which a window was broken. Unfortunately, the absence of radial or 1 to broken tempered glass. concentric fracture lines prevents these observations from being applied radial fracture A crack in a glass that extends outward like the spoke of a wheel from the point at which the glass was struck. concentric fracture A crack in a glass that forms a rough circle around the point of impact. 5 6FIGURE 9–15 8Radial and concentric fracture lines in a sheet of Tglass. S Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 224 CHAPTER 9 FIGURE 9–16 Crater-shaped hole made by a bullet passing through glass. The upper surface is the exit side of the projectile. Don Farrall/ Getty RF Images Inc. L I D D E L L , 1 (a) (b)5 6 FIGURE 9–17 8 Production of radial and concentric T are fractures in glass. (a) Radial cracks formed first, commencing onSthe side of Richard Saferstein, Ph.D. T I F F A N Y FIGURE 9–18 Stress marks on the edge of a radial glass fracture. Arrow indicates direction of force. the glass opposite to the destructive force. (b) Concentric cracks occur afterward, starting on the same side as the force. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 When there have been successive penetrations of glass, it is frequently possible to determine the sequence of impact by observing the existing fracture lines and their points of termination. A fracture always terminates at an existing line of fracture. In Figure 9–19, the fracture on the left preceded that on the right; we know this because the latter’s radial fracture lines terminate at the cracks of the former. MATTER, LIGHT, AND GLASS EXAMINATION 225 FIGURE 9–19 Two bullet holes in a piece of glass. The left hole preceded the right hole. L I D D E L L , ISBN: 978-1-323-16745-8 Collection and Preservation of Glass Evidence FIGURE 9–20 Presence of black tungsten oxide on the upper filament indicates that the filament was on when it was exposed to air. The lower filament was off, but its surface was coated with a yellow/white tungsten oxide, which was vaporized from the upper (“on”) filament and condensed onto the lower filament. T I F F A N Y The gathering of glass evidence at the crime scene and from the suspect must be thorough if the examiner is to have any chance of individualizing the fragments to a common source. If even the 1 effort must be made to colremotest possibility exists that fragments may be pieced together, every lect all the glass found. For example, evidence collection at hit-and-run 5 scenes must include all the broken parts of the headlight and reflector lenses. This evidence may ultimately prove invaluable in 6 with glass remaining in the placing a suspect vehicle at the accident scene by matching the fragments headlight or reflector shell of the suspect vehicle. In addition, examining the headlight’s filaments 8 may reveal whether an automobile’s headlights were on or off before the impact (see Figure 9–20). When an individual fit is improbable, the evidence collectorT must submit all glass evidence found in the possession of the suspect along with a sample of S broken glass remaining at the crime scene. This standard/reference glass should always be taken from any remaining glass in the window or door frames, as close as possible to the point of breakage. About one square inch of sample is usually adequate for this purpose. The glass fragments should be packaged in solid containers to avoid further breakage. If the suspect’s shoes and/or clothing are to be examined for the presence of glass fragments, they should be individually wrapped in paper and transmitted to the laboratory. The field investigator should avoid removing such evidence from garments unless absolutely necessary for its preservation. When a determination of the direction of impact is desired, all broken glass must be recovered and submitted for analysis. Wherever possible, the exterior and interior surfaces of the glass must be indicated. When this is not immediately apparent, the presence of dirt, paint, grease, or putty may indicate the exterior surface of the glass. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. chapter summary The forensic scientist must constantly determine the properties that impart distinguishing characteristics to matter, giving it a unique identity. Physical properties such as weight, volume, color, boiling point, and melting point describe a substance without reference to any other substance. A chemical property describes the behavior of a substance when it reacts or combines with another substance. Scientists throughout the world use the metric system of measurement. The metric system has basic units of measurement for length, mass, and volume: the meter, gram, and liter, respectively. Temperature is a measure of heat intensity, or the amount of heat in a substance. In science, the most commonly used temperature scale is the Celsius scale. This scale is derived by assigning the freezing point of water a value of 0°C and its boiling point a value of 100°C. To compare glass fragments, a forensic scientist evaluates two important physical properties: density and refractive index. Density is defined as the mass per unit volume. Refractive index is the ratio of the velocity of light in a vacuum to that in the medium under examination. Crystalline solids have definite geometric forms because of the orderly arrangement of their atoms. These solids refract a beam of light in two different light-ray components. This results in double refraction. Birefringence is the numerical difference between these two refractive indices. Not all solids are crystalline in nature. For example, glass has a random arrangement of atoms that forms an amorphous or noncrystalline solid. review questions T I F F A N Y 1 5 6 8 T S 9. A gas (has, has no) definite shape or volume. 10. During the process of ___________, solids go directly to the gaseous state, bypassing the liquid state. 11. The attraction forces between the molecules of a liquid are (greater, less) than those in a solid. 12. Different ___________ are separated by definite visible boundaries. 13. Mass per unit volume defines the property of ___________. 14. If an object is immersed in a liquid of greater density, it will (sink, float). 15. The bending of a light wave because of a change in velocity is called ___________. 16. The physical property of ___________ is determined by the ratio of the velocity of light in a vacuum to light’s velocity in a substance. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 1. Anything that has mass and occupies space is defined as ___________. 2. The basic building blocks of all substances are the ___________. 3. The number of elements known today is ___________. 4. An arrangement of elements by similar chemical properties is accomplished in the ___________ table. 5. A(n) ___________ is the smallest particle of an element that can exist. 6. Substances composed of two or more elements are called ___________. 7. A(n) ___________ is the smallest unit of a compound formed by the union of two or more atoms. 8. The physical state that retains a definite shape and volume is a(n) ___________. L I D D E L L , Dispersion is the process of separating light into its component colors. Each component bends, or refracts, at a different angle as it emerges from a prism. The large family of radiation waves is known as the electromagnetic spectrum. Two simple models explain light’s behavior. The first model describes light as a continuous wave; the second depicts light as a stream of energy particles. The flotation and immersion methods are best used to determine a glass fragment’s density and refractive index, respectively. In the flotation method, a glass particle is immersed in a liquid. The density of the liquid is carefully adjusted by the addition of small amounts of an appropriate liquid until the glass chip remains suspended in the liquid medium. At this point, the glass will have the same density as the liquid medium and can be compared to other relevant pieces of glass. The immersion method involves immersing a glass particle in a liquid medium whose refractive index is varied until it is equal to that of the glass particle. At this point, known as the match point, minimum contrast between liquid and particle is observed. By analyzing the radial and concentric fracture patterns in glass, the forensic scientist can determine the direction of impact. This can be accomplished by applying the 3R rule: Radial cracks form a Right angle on the Reverse side of the force. MATTER, LIGHT, AND GLASS EXAMINATION 17. True or False: Solids having an orderly arrangement of their constituent atoms are crystalline. ___________ 18. Solids that have their atoms randomly arranged are said to be ___________. 19. The crystal calcite has two indices of refraction. The difference between these two values is known as ___________. 20. The process of separating light into its component colors or frequencies is known as ___________. 21. True or False: Color is a usual indication that substances selectively absorb light. ___________ 22. The distance between two successive identical points on a wave is known as ___________. 23. True or False: Frequency and wavelength are directly proportional to one another. ___________ 24. Light, X-rays, and radio waves are all members of the ___________ spectrum. 25. Red light is (higher, lower) in frequency than violet light. 26. A beam of light that has all of its waves pulsating in unison is called a(n) ___________. 27. One model of light depicts it as consisting of energy particles known as ___________. 28. True or False: The energy of a light particle (photon) is directly proportional to its frequency. ___________ 29. Red light is (more, less) energetic than violet light. 30. A hard, brittle, amorphous substance composed mainly of silicon oxides is ___________. 31. Glass that can be physically pieced together has ___________ characteristics. 32. The two most useful physical properties of glass for forensic comparisons are ___________ and ___________. 33. True or False: Automobile headlights and heat-resistant glass, such as Pyrex, are manufactured with lime oxide added to the oxide mix. ___________ ISBN: 978-1-323-16745-8 review questions for inside 1. A(n) ___________ property describes the behavior of a substance without reference to any other substance. 2. A(n) ___________ property describes the behavior of a substance when it reacts or combines with another substance. 3. The ___________ system of measurement was devised by the French Academy of Science in 1791. 227 34. ___________ glass fragments into small squares, or “dices,” with little splintering when broken. 35. ___________ glass gains added strength from a layer of plastic inserted between two pieces of ordinary window glass; it is used in automobile windshields. 36. Comparing the relative densities of glass fragments is readily accomplished by a method known as ___________. 37. When glass is immersed in a liquid of similar refractive index, its ___________ disappears and minimum contrast between the glass and liquid is observed. 38. The exact numerical density and refractive indices of glass can be correlated to ___________ in order to asL sess the evidential value of the comparison. I 39. D D 40. E 41. L L 42. , The fracture lines radiating outward from a crack in glass are known as ___________ fractures. A crater-shaped hole in glass is (narrower, wider) on the side where the projectile entered the glass. True or False: It is easy to determine from the size and shape of a hole in glass whether it was made by a bullet or some other projectile. ___________ True or False: Stress marks on the edge of a radial crack are always perpendicular to the edge of the surface on which the impact force originated. ___________ T 43. I 44. F F 45. A N 46. Y A fracture line (will, will not) terminate at an existing line fracture. Glass fracture lines that encircle the hole in the glass are known as ___________ fractures. When glass’s elastic limit is exceeded, the first fractures develop into radial lines on the surface of the (same, opposite) side to that of the penetrating force. Collected glass fragment evidence should be packaged in ___________ containers to avoid further breakage. 47. Glass-containing shoes and/or clothing should be individually wrapped in ___________ and transmitted to the laboratory. 1 5 6 8 T the S science 4. The basic units of measurement for length, mass, and volume in the metric system are the ___________, ___________, and ___________, respectively. 5. A centigram is equivalent to ___________ gram(s). 6. A milliliter is equivalent to ___________ liter(s). 7. 0.2 gram is equivalent to ___________ milligram(s). 8. One cubic centimeter (cc) is equivalent to one ___________. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 228 CHAPTER 9 9. True or False: One meter is slightly longer than a yard. ___________ 10. The equivalent of 1 pound in grams is ___________. 14. There are ___________ degrees Celsius between the freezing and boiling points of water. 15. The amount of matter an object contains determines its ___________. 16. The simplest type of balance for weighing is the ___________. 11. True or False: A liter is slightly larger than a quart. ___________ 12. ___________ is a measure of a substance’s heat intensity. 13. There are ___________ degrees Fahrenheit between the freezing and boiling points of water. L application and critical thinking 1. An accident investigator arrives at the scene of a hitand-run collision. The driver who remained at the scene reports that the windshield or a side window of the car that struck him shattered on impact. The investigator searches the accident site and collects a large number of fragments of tempered glass. This is the only type of glass recovered from the scene. How can the glass evidence help the investigator locate the vehicle that fled the scene? 2. Indicate the order in which the bullet holes were made in the glass depicted in the accompanying figure. Explain the reason for your answer. (a) I D D E L L , 3. The accompanying figure depicts stress marks on the edge of a glass fracture caused by the application of force. If this is a radial fracture, from which side of the glass (left or right) was the force applied? From which side was force applied if it is a concentric fracture? Explain the reason for your answers. T I F F A N Y 1 5 6 8 T S (b) (c) ISBN: 978-1-323-16745-8 Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. MATTER, LIGHT, AND GLASS EXAMINATION 229 further references Bottrell, M. C., “Forensic Glass Comparison: Background Information Used in Data Interpretation,” Forensic Science Communications 11, no. 2 (2009), http://www .fbi.gov/about-us/lab/forensic-science-communications/ fsc/april2009. Caddy, B., ed., Forensic Examination of Glass and Paint. Boca Raton, Fla.: CRC Press, 2001. Koons, R. D., J. Buscaglia, M. Bottrell, and E. T. Miller, “Forensic Glass Comparisons,” in R. Saferstein, ed., Forensic Science Handbook, vol. 1, 2nd ed. Upper Saddle River, N.J.: Prentice Hall, 2002. Thornton, J. I., “Interpretation of Physical Aspects of Glass Evidence,” in B. Caddy, ed., Forensic Examination of Glass and Paint. Boca Raton, Fla.: CRC Press, 2001. L I D D E L L , T I F F A N Y ISBN: 978-1-323-16745-8 1 5 6 8 T S Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. headline news Jeffrey MacDonald: Fatal Vision The grisly murder scene that confronted police on February 17, 1970, is one that cannot AP Im ages be wiped from memory. Summoned to the Fort Bragg L of Captain Jeffrey MacDonald, a physician, police residence found the I bludgeoned body of MacDonald’s wife. She had been D repeatedly knifed, and her face was smashed to a pulp. D MacDonald’s two children, ages 2 and 5, had been brutally and repeatedly knifed and battered to E death. Suspicion quickly fell on MacDonald. To the L eyes of investigators, the murder scene had a staged L appearance. MacDonald described a frantic effort ,to subdue four intruders who had slashed at him with an ice pick. However, the confrontation left TMacDonald with minor wounds and no apparent I defense wounds on his arms. MacDonald then F described how he had covered his slashed F wife with his blue pajama top. Interestingly, when the body was removed, blue threads A were observed under the body. In fact, blue N threads matching the pajama top turned Y up throughout the house—nineteen in one child’s bedroom, including one beneath 1 and two in the other child’s bedroom. her fingernail, Eighty-one blue fibers5were recovered from the master bedroom, and two were located on a bloodstained 6 piece of wood outside the house. Later forensic examination showed that the 48 ice pick holes8in the pajama top were smooth and cylindrical, a sign that the top was stationary when it was slashed. Also, folding the pajama top demonstrated that T the 48 holes actually could have been made by 21 thrusts of an ice pick. This coincided with the number S of wounds that MacDonald’s wife sustained. As described in the book Fatal Vision, which chronicled the murder investigation, when MacDonald was confronted with adulterous conduct, he replied, “You guys are more thorough than I thought.” MacDonald is currently serving three consecutive life sentences. ISBN: 978-1-323-16745-8 Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. chapter 10 hairs and fibers Learning Objectives L I D D E L L , After studying this chapter you should be able to: T and medulla t Recognize and understand the cuticle, cortex, I areas of hair F t List the three phases of hair growth t Appreciate the distinction between animalFand human hairs A t List hair features that are useful for the microscopic N comparison of human hairs Y evidence t Explain the proper collection of forensic hair t Describe and understand the role of DNA typing in hair 1 comparisons KEY TERMS anagen phase catagen phase cortex cuticle follicular tag macromolecule manufactured fibers medulla mitochondrial DNA molecule monomer natural fibers nuclear DNA polymer telogen phase 5 and manufactured t Understand the differences between natural fibers 6 8 t List the properties of fibers that are most useful for forensic comparisons T ISBN: 978-1-323-16745-8 t Describe the proper collection of fiber evidence S Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. 232 CHAPTER 10 The trace evidence transferred between individuals and objects during the commission of a crime, if recovered, often corroborates other evidence developed during the course of an investigation. Although in most cases physical evidence cannot by itself positively identify a suspect, laboratory examination may narrow the origin of such evidence to a group that includes the suspect. Using many instruments and techniques, the crime laboratory has developed a variety of procedures for comparing and tracing the origins of physical evidence. This chapter and those that follow discuss how to apply these techniques to the analysis of the types of physical evidence most often encountered at crime scenes. We begin with a discussion of hairs and fibers. Forensic Examination of Hair Hair is encountered as physical evidence in a wide variety of crimes. However, any review of the forensic aspects of hair examination L must start with the observation that it is not yet possible to individualize a human hair to any single head or body through its morphology. Over the years, criminalists have tried to isolateI the physical and chemical properties of hair that could serve as individual characteristics of identity. D Partial success has finally been achieved by isolating and characterizing the DNA present in hair. D The importance of hair as physical evidence cannot be underemphasized. Its removal from the body often denotes physicalEcontact between a victim and perpetrator and hence a crime of a serious or violent nature. When hair is properly collected at the crime scene and submitted to Lstandard/reference samples, it can provide strong corroborative the laboratory along with enough evidence for placing an individual L at a crime site. The first step in the forensic examination of hair logically starts with its color and structure, , progresses to the more detailed DNA extraction, isolation, and or morphology, and, if warranted, characterization. cuticle The scale structure covering the exterior of the hair. cortex The main body of the hair shaft. medulla A cellular column running through the center of the hair. T Morphology of I Hair F that grows out of an organ known as the hair follicle. The Hair is an appendage of the skin length of a hair extends fromFits root or bulb embedded in the follicle, continues into the shaft, and terminates at the tip end. The shaft, which is composed of three layers—the cuticle, A to the most intense examination by the forensic scientist cortex, and medulla—is subjected (see Figure 10–1). N Y Cortex Cuticle Follicle Root 1 5 6 8 T S Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 FIGURE 10–1 Cross section of skin showing hair growing out of a tubelike structure called the follicle. HAIRS AND FIBERS 233 Cuticle Two features that make hair a good subject for establishing individual identity are its resistance to chemical decomposition and its ability to retain structural features over a long period of time. Much of this resistance and stability is attributed to the cuticle, the outside covering of the hair. The cuticle is formed by overlapping scales that always point toward the tip end of each hair. The scales form from specialized cells that have hardened (keratinized) and flattened in progressing from the follicle. There are three basic patterns that describe the appearance of the cuticle: cornal, spinous, and imbricate (see Figure 10–2). The scales of most animal hair can best be described as looking like shingles on a roof. Although the scale pattern is not a useful characteristic for individualizing human hair, the variety of patterns formed by animal hair makes it an important feature for species identification. Figure 10–3 shows the scale patterns of some animal hairs and of a human hair as viewed by the scanning electron microscope. Another method of studying the scale pattern of hair is to make L medium, such as clear nail a cast of its surface. This is done by embedding the hair in a soft polish or softened vinyl. When the medium has hardened, the hair is removed, leaving a clear, I distinct impression of the hair’s cuticle, ideal for examination with a compound microscope. D D Contained within the protective layer of the cuticle is the cortex. The cortex is made up of spindle-shaped cortical cells aligned in a regular array, parallelEto the length of the hair. The cortex derives its major forensic importance from the fact that it is embedded with the pigment L granules that give hair its color. The color, shape, and distribution of these granules provide imL portant points of comparison among the hairs of different individuals. The structural features of the cortex are examined microscopically after the hair has been , mounted in a liquid medium with a refractive index close to that of the hair. Under these condiCortex tions, the amount of light reflected off the hair’s surface is minimized, and the amount of light penetrating the hair is optimized. T Medulla I Richard Saferstein, Ph.D. The medulla is a collection of cells that looks like a central canal running through a hair. In many F animals, this canal is a predominant feature, occupying more than half of the hair’s diameter. The Fthe diameter of the hair shaft medullary index measures the diameter of the medulla relative to (a) A FIGURE 10–2 N (a) The coronal, or crownlike, scale pattern Y resembles a stack of paper cups. (b) Spinous or petal-like scales are triangular in shape and protrude from the hair shaft. (c) The 1 imbricate, or flattened-scale, type consists of overlapping scales 5 with narrow margins. 6 8 T S ISBN: 978-1-323-16745-8 (b) (c) Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. Richard Saferstein, Ph.D. Richard Saferstein, Ph.D. L (b) I D D E L L , (c) Richard Saferstein, Ph.D. (a) (d) Continuous FIGURE 10–4 Medulla patterns. The initial growth phase during which the hair follicle actively produces hair. (f) Interrupted Fragmented and is normally expressed as a fraction. For humans, the index is generally less than one-third; 1 is one-half or greater. for most other animals, the index The presence and appearance of the medulla vary from individual to individual and even 5 among the hairs of a given individual. Not all hairs have medullae, and when they do exist, the degree of medullation can vary.6In this respect, medullae may be classified as being continuous, interrupted, fragmented, or absent (see Figure 10–4). Human head hairs generally exhibit no me8 dullae or have fragmented ones; they rarely show continuous medullation. One noted exception T is the Mongoloid race, whose members usually have head hairs with continuous medullae. Also, most animals have medullae that are either continuous or interrupted. S Another interesting feature of the medulla is its shape. Humans, as well as many animals, have medullae that give a nearly cylindrical appearance. Other animals exhibit medullae that have a patterned shape. For example, the medulla of a cat can best be described as resembling a string of pearls, whereas members of the deer family show a medullary structure consisting of spherical cells occupying the entire hair shaft. Figure 10–5 illustrates medullary sizes and forms for a number of common animal hairs and a human head hair. A searchable database on CD-ROM of the 35 most common animal hairs encountered in forensic casework is commercially available.1 This database allows an examiner to rapidly search 1 J. D. Baker and D. L. Exline, Forensic Animal Hair Atlas: A Searchable Database on CD-ROM. RJ Lee Group, Inc., 350 Hochberg Rd., Monroeville, PA, 15146. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 anagen phase T (e) I F F A N Y Richard Saferstein, Ph.D. FIGURE 10–3 Scale patterns of various types of hair. (a) Human head hair (600×), (b) dog (1250×), (c) deer (120×), (d) rabbit (300×), (e) cat (2000×), and (f) horse (450×). Richard Saferstein, Ph.D. CHAPTER 10 Richard Saferstein, Ph.D. 234 (a) (b) 235 Richard Saferstein, Ph.D. L I D D E L L , Richard Saferstein, Ph.D. Richard Saferstein, Ph.D. HAIRS AND FIBERS (c) ISBN: 978-1-323-16745-8 1 5 6 (d) (e) (f) 8 FIGURE 10–5 Medulla patterns for various types of hair. (a) Human head T hair (400×), (b) dog (400×), (c) deer (500×), (d) rabbit (450×), (e) cat (400×), and (f) mouse (500×). S for animal hairs based on scale patterns and/or medulla type using a PC. A typical screen presentation arising from such a data search is shown in Figure 10–6. Root The root and other surrounding cells within the hair follicle provide the tools necessary to produce hair and continue its growth. Human head hair grows in three developmental stages, and the shape and size of the hair root is determined by the growth phase in which the hair happens to be. The three phases of hair growth are the anagen, catagen, and telogen phases. catagen phase A transition stage between the anagen and telogen phases of hair growth. telogen phase The final growth phase in which hair naturally falls out of the skin. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. Richard Saferstein, Ph.D. Richard Saferstein, Ph.D. Richard Saferstein, Ph.D. T I F F A N Y 236 CHAPTER 10 RJ Lee Group L I D D E L L , FIGURE 10–6 Information on rabbit hair contained within the Forensic Animal Hair Atlas. (b) 1 5 6 (c) 8 FIGURE 10–7 Hair roots in the (a) anagen phase, (b) catagen phase, and (c) telogen phase (100×). T S follicular tag In the anagen phase, which may last up to six years, the root is attached to the follicle for continued growth, giving the root bulb a flame-shaped appearance (Figure 10–7[a]). When pulled from the root, some hairs in the anagen phase have a follicular tag. With the advent of DNA analysis, this follicular tag is important for individualizing hair. Hair continues to grow, but at a decreasing rate, during the catagen phase, which can last anywhere from two to three weeks. In the catagen phase, roots typically take on an elongated appearance (Figure 10–7[b]) as the root bulb shrinks and is pushed out of the hair follicle. Once hair growth ends, the telogen phase begins and the root takes on a club-shaped appearance (Figure 10–7[c]). Over two to six months, the hair is pushed out of the follicle, causing the hair to be naturally shed. Criminalistics: An Introduction to Forensic Science, Eleventh Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2015 by Pearson Education, Inc. ISBN: 978-1-323-16745-8 A translucent piece of tissue surrounding the hair’s shaft near the root; it contains the richest source of DNA associated with hair. Courtesy of Charles A. Linch (a) T I F F A N Y HAIRS AND FIBERS 237 Identification and Comparison of Hair Most often the prime purpose for examining hair evidence in a crime laboratory is to establish whether the hair is human or animal in origin or to determine whether human hair retrieved at a crime scene compares with hair from a particular individual. Although animal hair can normally be distinguished from human hair with little difficulty, human hair comparisons must be undertaken with extreme caution and with an awareness of hair’s tendency to exhibit variable morphological characteristics, not only from one person to another but also within a single individual. Considerations in Hair Examination A careful microscopic examination of hair reveals morphological features that can distinguish human hair from animal hair. The hair of various animals also differs enough in structure that the examiner can often identify the species. Before reaching such a conclusion, however, the examiner must have access to a comprehensive collection of referenceL standards and the accumulated experience of hundreds of prior hair examinations. Scale structure, medullary index, and medulI lary shape are particularly important in hair identification. The most common request when hair is used as forensic evidence D is to determine whether hair recovered at the crime scene compares to hair removed from a suspect. In most cases, such a comparison relates to hair obtained from the scalp or pubic area. D Ultimately, the evidential value of the comparison depends on the degree of probability with which E the examiner can associate the hair in question with a particular individual. L In making a hair comparison, a comparison microscope is an L and known hair together, invaluable tool that allows the examiner to view the questioned side by side. Any variations in the microscopic characteristics ,will thus be readily observed. Because hair from any part of the body exhibits a range of characteristics, it is necessary to have an adequate number of known hairs that are representative of all of its features when making a comparison. T In comparing hair, the criminalist is particularly interested in matching the color, length, and diameter. Other important features are the presence or absence ofI a medulla and the distribution, shape, and color intensity of the pigment granules in the cortex. AFmicroscopic examination may also distinguish dyed or bleached hair from natural hair. A dyed color is often present in the cuticle as well as throughout the cortex. Bleaching, on the other hand,Ftends to remove pigment from the hair and to give it a yellowish tint. If hair has grown since itA was last bleached or dyed, the natural-end portion will be quite distinct in color. An estimate of the time since dyeing or bleachN ing can be made because hair grows approximately one centimeter per month. Other significant but less frequent features may be observed in hair. For example, Ymorphological abnormalities may be present because of certain diseases or deficiencies. Also, the presence of fungal and nit infections can further link a hair specimen to a particular individual. HAIR CHARACTERISTICS 1 5 against standard/reference an appropriate approach for including and excluding questioned hairs hairs, many forensic scientists have long recognized that this approach is subjective and is 6 highly dependent on the skills and in...
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What was Shipman's murder weapon of choice and how did this weapon allow him to
go undetected for so many years?
Shipman's weapon was Morphine, and the doctor's first victim was Eva Lyons who was
killed in 1975 while the doctor was working at the Abraham Ormerod medical practice in
Todmorden. Shipman built his reputation as a respectable general practitioner, and his patients
grew accustomed to his practice, and in the process, he gave them injections for their respective
medication furthermore they saw it as nothing but an ordinary injection which was, in turn, a
lethal injection. Dr. Shipman has the perfect cover of everyone's trust, and he could get to his
patients with ease and in the process cover for their death by signing their death certificate, and
no one would question his actions. The doctor went ahead to use the morphine drug to kill 71
patients while at the Donnebrool practice. In his endeavors, the doctor obtained enough
morphine to kill over 360 people, and on the same account, his method of murder was consistent
and thus making a perfect cover and, in the process, staying law for so long undetected. Most of
the doctor’s patients and victims were women and old people and, in this case, it made much
more sense since these individuals could not put up a fight and thus this made his crimes
relatively easy to perpetrate (Saferstein, 2015).
After being discovered for forging prescription Dr. Shipman was fired from the Todmorden
medical practice, he received a hefty fine but did not have his license revoked by the General
Medical Council which was a regulatory body for medi...


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