Criminal Law. A principal in the first degree is one who commits the crime by his own hand, by an inanimate agency, or through an innocent party. If X stabs V, then X is the principal in the first degree. If X poisons V’s favorite scotch and V dies from the poison, then, even if X is not present, X is the principal first. And suppose X, knowing that P suffers from paranoid delusions, gives P a gun and tells P that V is coming to kill him. If X then invites V over to visit P, who subsequently shoots V, X may be a principal in V’s murder if P is determined to be an innocent agent.
More than one person may be first-degree principals to the crime, if they all participate in the criminal act. For instance, if X and Y alternately stab V, who dies from a loss of blood, both X and Y are principals first.