The key concept in criminal law is INTENT. INTENT is the mental state of a person when they commit a crime, and it is an essential element in determining whether or not a person is guilty of a crime. INTENT is often difficult to prove, as it requires evidence of the accused's state of mind at the time of the crime. INTENT is also important in determining the severity of the punishment for a crime, as it can be used to distinguish between premeditated and accidental crimes.