This issue first came before the courts in the Middle Ages. By the 14th century, the law determined that children under seven did not have the capacity to commit a crime. By seven they developed an "age of reason" and responsibility. Many states have codified this into common law rules. However, the laws often vary based on ages. In most states, people around 14 years of age are inferred to be capable of formulating the necessary frame of mind to commit a crime. However, it can be shown otherwise in a court, so this is not a hard and fast rule.