accomplice, confederate (noun)
a person who joins with another in carrying out some plan (especially an unethical or illegal plan)
An associate in the commission of a crime; a participator in an offense, whether a principal or an accessory.
At law, an accomplice is a person who actively participates in the commission of a crime, even though they take no part in the actual criminal offense. For example, in a bank robbery, the person who points the gun at the teller and asks for the money is guilty of armed robbery. However, anyone else directly involved in the commission of the crime, such as the lookout or the getaway car driver, is an accomplice, even though in the absence of an underlying offense keeping a lookout or driving a car would not be an offense. An accomplice differs from an accessory in that an accomplice is present at the actual crime, and could be prosecuted even if the main criminal is not charged or convicted. An accessory is generally not present at the actual crime, and may be subject to lesser penalties than an accomplice or principal. An accomplice was often referred to as an abettor. This term is not in active use in the United States, having been replaced by accomplice. At law, an accomplice has the same degree of guilt as the person he or she is assisting, is subject to prosecution for the same crime, and faces the same criminal penalties. As such, the three accomplices to the bank robbery above can also be found guilty of armed robbery even though only one stole money.