Of greatest importance. 2 n. One who authorizes another to act in his or her behalf as an agent; any person involved in the commission of a criminal act. disclosed.A principal whose identity is shared by his or her agent with the third party. principal in the first degree. The actual perpetrator of a crime. principal in the second degree. Someone who assists in some way the principal in the first degree. undisclosed.A principal whose identity is kept secret by his agent. Both the undisclosed ...