Criminal Law. A principal in the second degree is one actually or constructively present at the scene of a crime who aids, counsels, commands, or encourages its commission. For example, a principal second may be one who stands by with a gun while the principal in the first degree shoots one of the victims. The principal in the second degree need not be actually present at the commission of the crime if he is aiding the principal and is close enough to render assistance if needed. The actor’s constructive presence implicates him as long as he plays an active role in the crime, such as being either a lookout or a driver of the getaway car.