A crime usually needs two things at once: a guilty act and a guilty mind
Most crimes require proof of both actus reus, the guilty act, and mens rea, the guilty mind. Swing a belt at one person, miss, and hit a bystander, and the law simply moves your intent onto the person you actually struck. That rule, transferred malice, is one of many ways criminal law reasons about blame.
Criminal law covers conduct seen as threatening or harmful to people's property, health, safety and welfare, and most of it is written by legislatures. It differs from civil law, which focuses more on settling disputes and compensating victims than on punishment. Early societies rarely separated the two. The Code of Ur-Nammu, from around 2100 to 2050 BC, is the earliest surviving written legal code, though an older code of Urukagina of Lagash is known to have existed, and Hammurabi's code formed the core of Babylonian law.
Roman jurists still treated theft as a tort paid off with compensation, but the revival of Roman law in the twelfth century supplied the categories Europe later used to split criminal from civil matters. The idea of a distinct criminal penalty grew out of Spanish late scholastic theology, where divine punishment for a guilty mind passed into church law and then into secular law. Courts run by the state, backed by police forces, took clear shape in eighteenth-century Europe.
Punishment is usually justified by five aims: retribution, deterrence, incapacitation, rehabilitation and restoration, weighted differently by each jurisdiction. Restoration looks to the victim; an embezzler, for example, may be ordered to repay what was taken.
The guilty act can be an action, a threat or, exceptionally, a failure to act where a duty exists, such as a parent's duty to feed a young child. Causation matters: the act must be a real cause of the harm, and under the thin skull rule a victim's unusual frailty does not excuse the offender, while an unforeseeable intervening event can break the chain. The mental element ranges from intent through recklessness; knowingly accepting a serious risk can be enough. Some modern regulatory offences drop the mental element entirely. In Britain, driving over the alcohol limit under the Road Traffic Act 1988 is a strict liability offence.
Source: Criminal law
