Meet the cop who busted scumbags by day — and Satan by night.

The new horror film “Deliver Us From Evil,” due in theaters July 2, is based on the accounts of a real NYPD sergeant, Ralph Sarchie, who spent many years on the force while assisting with exorcisms in his spare time.

In this exclusive clip from a forthcoming 15-minute documentary about Sarchie, he talks about his real-life experiences investigating demonic possessions. He worked in the company of a breakaway Catholic priest who split with the church over exorcisms.

Sarchie, who wrote a 2001 book about his demon-chasing career called “Beware the Night,” says he assisted at more than 20 such rituals, and investigated more than 50 spooky cases in all. He and his crew would typically roam a spirit-infested house to spread holy water, incense and holy oil, then pray in unison.

Is Sarchie’s story credible? You make the call.