We've all seen our share of exorcisms in the movies and on TV: But what is it like to experience one in real life? We decided to find out.

Inspired by our partnership with the movie Incarnate , The Lineup sat down with demonologist Al Willen, who has been present for and assisted with exorcisms throughout his 50-year career. A third-generation demonologist, Willen was trained in the ways of demonology and exorcism by his grandfather, a religious demonologist who studied at the Vatican. Willen currently works throughout the New York area, examining individuals for signs of possession, debunking cases, and, when necessary, participating in exorcisms.

In part one of a three part series, we asked Willen in what ways exorcisms portrayed in the movies are different than real-life exorcisms, what the symptoms of demonic possession look like, and how, specifically, he is able to determine when someone is possessed.