A criminal accomplice is a person who knowingly, voluntarily, or intentionally assists another person in the commission of a crime—or under some circumstances, a person who fails to prevent another person from committing a crime. Unlike a person who aids and abets a crime by helping with the planning of the crime but is often not present at the scene of the crime—and unlike an accessory after the fact, who is not present at the scene of the crime but assists after the commission of the crime to help the perpetrator avoid arrest or punishment—an accomplice actively participates in the commission of the crime. For example, a person who acts as a lookout or getaway driver for a bank robbery is an accomplice.

In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a bank robbery that resulted in a death.

In New Jersey, the concept of an accomplice is covered under the state's accomplice liability laws. An individual is considered an accomplice if they purposely aid, agree to aid, or attempt to aid another person in planning or committing a crime. This includes being a lookout, getaway driver, or any other form of active participation. New Jersey law does not require the accomplice to be physically present at the crime scene to be held liable. Under the New Jersey Code of Criminal Justice, accomplices are generally treated the same as the person who actually committed the criminal act, meaning they can face the same charges and penalties as the principal offender. This includes serious offenses where the felony murder rule applies; if a death occurs during the commission of certain felonies, such as a bank robbery, an accomplice can be charged with first-degree murder, even if their role did not involve directly causing the death.