CHICAGO (AP) — A pharmacologist testifying in the trial of a white Chicago police officer charged with murder in the shooting of Laquan McDonald says PCP in the black teen’s system could have caused aggression, rage and hallucinations.

James Thomas O’Donnell said during Van Dyke’s murder trial on Thursday that that someone with as much of PCP in his system as McDonald had in his bloodstream could have a “feeling of omnipotence.” O’Donnell said the person could feel as if he has “superhuman powers.” He says that could put a person at risk of harming himself or others around him.

Other witnesses have testified that McDonald refused to drop a knife as police ordered and that McDonald stabbed the tire of a police vehicle. O’Donnell said such “violent rage behavior” could be explained by having PCP in his system.

Under cross examination, O’Donnell acknowledged that he had no information that Van Dyke knew McDonald had PCP in his system when he shot him 16 times on the night of Oct. 20, 2014.