Criminal liability is to be found in relation not only to those who perform the final causative act, but also those who contribute before the act. The law deals differently in relation to complicity depending on the seriousness of the offence. Offences are grouped into two categories, those being felonies and misdemeanours.
Complicity in Felonies
The perpetrator of a felony is known, for these purposes, as the principal in the first degree. There can be more than one principal in the first degree.
A principal in the second degree is someone present at the crime scene who aids and abets or acts as an accomplice to the crime.
Then there are accessories, or accessorial offences. An accessory before the fact is a person who assists in preparation or who procures or commands the commission of the crime. An accessory after the fact aids the direct perpetrator during the period after the offence. They know the crime has been committed and they assist the offender(s) to avoid police capture.
Complicity in Misdemeanours
The perpetrator of a misdemeanour is simply known as the perpetrator. There can be more than one perpetrator. All others involved in the matter are known as accomplices. There are no accessories after the fact at common law, although some codified criminal law systems do include them as offenders.