Intoxication in English law is a circumstance which may alter the capacity of a defendant to form mens rea, where a charge is one of specific intent, or may entirely negate mens rea where the intoxication is involuntary. The fact that a defendant is intoxicated in the commission of a crime — whether voluntarily or not — has never been regarded as a full defence to criminal proceedings (unlike statutory defences such as self defence). Its development at common law has been shaped by the acceptance that intoxicated individuals do not think or act as rationally as they would otherwise, but also by a public policy necessity to punish individuals who commit crimes.