Since I have never met him personally, I cannot say whether he is possessed by demons or not. In Scripture, a demon-possessed person can manifest a variety of extreme behaviors.Some of these passages, the demon possession causes physical ailments such as inability to speak, epileptic symptoms, blindness, etc. In other cases, it causes the individual to do evil, Judas being the main example. In Acts 16:16-18, the spirit apparently gives a slave girl some ability to know things beyond her own learning. The demon-possessed man of the Gadarenes, who was possessed by a multitude of demons (Legion), had superhuman strength and lived naked among the tombstones. King Saul, after rebelling against the LORD, was troubled by an evil spirit (1 Samuel 16:14-15; 18:10-11; 19:9-10) with the apparent effect of a depressed mood and an increased desire to kill David.
These behaviors do not seem to be consistent with Criss Angel's. The most likely explanation is that Criss is an optical illusionist and an entertainer. He may be tapping into the occult and be under the influence of demons, but no one can be absolutely sure. Read this previous post here for more information. Hope this helps.
[Answered by Pastor HM]
