An accessory, in the context of criminal law, is a person who helps in the commission of a crime, such as by commanding the crime, driving the getaway car, providing the weapons, assisting in the planning, providing an alibi, or hiding the main offender after the crime. The accessory may or may not be present during the crime, but must be aware that the crime is going to be committed or has been committed.
A principal offender cannot also be an accessory. The punishment for an accessory is usually lighter than for the principal offender. A criminal charge of aiding and abetting or accessory can usually be brought against anyone who helps in the commission of a crime, though legal distinctions vary by state.