The main significance of the distinction is that generally, the accomplice may not be convicted unless the prosecution also proves that the principal is guilty of the substantive crime in question. The most important rule to remember in dealing with accomplices is that generally, the accomplice is guilty of the substantive crimes he assisted or encouraged. The key principle of accomplice liability is that one who aids , abets , encourages or assists another to perform a crime, will himself be liable for that crime . A is guilty of bank robbery, even though he did not himself use any violence, or even set foot inside the bank or touch the money. A encourages B to kill V, and supplies B with a rifle with which to do the deed.
B kills V with the rifle.
That is, the requisite encouragement, assistance, etc., may all take place before the actual occasion on which the crime takes place. The prosecution must also show that D was at the crime scene for the purpose of approving and encouraging commission of the offense. But D's presence at the crime scene can, of course, be convincing circumstantial evidence that D encouraged or assisted the crime. Normally, the mere fact that D failed to intervene to prevent the crime will not make him an accomplice, even if the intervention could have been accomplished easily. B decides to shoplift a ring from a sidewalk vendor.