Criminal law is the body of law that defines criminal offences and the penalties for convicted offenders.[13] Apprehending, charging, and trying suspected offenders is regulated by the law of criminal procedure.[14] The paradigm case of a crime lies in the proof, beyond reasonable doubt, that a person is guilty of two things. First, the accused must commit an act which is deemed by society to be criminal, or actus reus (guilty act).[15] Second, the accused must have the requisite malicious intent to do a criminal act, or mens rea (guilty mind). However for so called "strict liability" crimes, which include cases like dangerous driving, proof of mens rea is not necessary. An actus reus is enough.[16]
Examples of different kinds of crime include murder, assault, fraud or theft. In exceptional circumstances, defences can exist to some crimes, such as killing in self defence, or pleading insanity. Another example is in the 19th century English case of R v. Dudley and Stephens,[17] which tested a defence of "necessity". The Mignotte, sailing from Southampton to Sydney, sank. Three crew members and a cabin boy were stranded on a raft. They were starving and the cabin boy was close to death. Driven to extreme hunger, the crew killed and ate the cabin boy. The crew survived and were rescued, but put on trial for murder. They argued it was necessary to kill the cabin boy to preserve their own lives. Lord Coleridge, expressing immense disapproval, ruled, "to preserve one's life is generally speaking a duty, but it may be the plainest and the highest duty to sacrifice it." The men were sentenced to hang, but public opinion, especially among seafarers, was outraged and overwhelmingly supportive of the crew's right to preserve their own lives. In the end, the Crown commuted their sentences to six months in jail.
Criminal law offences are viewed as offences against not just individual victims, but the community as well.[13] The state, usually with the help of police, takes the lead in prosecution, which is why in common law countries cases are cited as "The People v. …" or "R. (for Rex or Regina) v. …" Also, lay juries are often used to determine the guilt of defendants on points of fact: juries cannot change legal rules. Some developed countries still condone capital punishment for criminal activity, but the normal punishment for a crime will be imprisonment, fines, state supervision (such as probation), or community service. Modern criminal law has been affected considerably by the social sciences, especially with respect to sentencing, legal research, legislation, and rehabilitation.[13] On the international field, 105 countries have signed the enabling treaty for the International Criminal Court, which was established to try people for crimes against humanity.[18]
