Criminal law is a major field of law that is focused on protecting society from criminality such as murder, robbery, rape, fraud, and embezzlement. An important characteristic of criminal law that differentiates it from civil law is that the prosecution is conducted by the state or government. A trial may result in a wide variety of different punishments, including imprisonment, probation, community service, or simply a fine, depending on the crime’s level of seriousness and its impact on society. For instance, while battery and shoplifting both fall under the category of criminal law, naturally, courts are more likely to treat battery as a more serious offense towards society and as a result, pass a more severe punishment or judgement.
The foundation of criminal law is based on mens rea and actus reus, which in Latin mean ‘state of mind’ and ‘actual act’, respectively. This is extremely important, as it defines how prosecutors can proceed with a case against a defendant. As soon as a case is brought to a prosecutor's attention, it becomes critical to assess the level of voluntariness, which is the level of intentionality in committing the crime. A good example to illustrate this is the distinction made between murder and manslaughter. While in the former there is intentionality in committing murder, the death of an individual is deemed manslaughter if a person’s actions unintentionally result in the death, such as drunk driving.
Intentionality and a person’s state of mind when the crime was committed contribute to the complexity of criminal law. Defense lawyers are able to use mens rea and actus reus to a such a high degree, that an acquittal can be possible. For instance, if an individual is charged with murder, and their defense lawyer is able to prove that the defendant lacked the prerequisite mens rea, the charge of murder may be reduced to manslaughter. Similarly, if a defendant is proven to have lacked the awareness or consciousness of the seriousness of the crime, the charges may be altered or even dropped. This is the reason many defense lawyers attempt to use an insanity defense, which while might be difficult to prove, is extremely effective is actually proven.
While criminal law in the United States is focused on retribution for crimes committed, there has been a recent push for greater focus on criminal rehabilitation, which has been successful to a certain degree in other countries, most notably Sweden and Norway.