10 Horror Movie Facts That Will Blow Your Mind

Finally, if you wanted anymore confirmation that The Exorcist is one of the scariest horror movies of all time, then this little tidbit should do it for you. Not only terrifying on screen, but in real life too, the set had an actual, bona fide murderer walking around as an extra that we see during Regan's stint in hospital. Yikes.

But how on Earth did that happen? Well, Paul Bateson was working as a radiological technician at the time of filming. When director William Friedkin went hunting for locations at the Tisch Hospital, Bateson was front and centre for his work performing a cerebral angiography - the very treatment that Friedkin witnessed and decided to put into his movie.

Friedkin wanted the procedure recreated as closely as possible, so used the doctors, assistants, and their hospital for two weekends to capture one of the most widely-recognised and medically accurate horror moments from the movie. Bateson was the radiologist on screen that directs Regan, but he had a far different life outside of his time at work.

Bateson was arrested a few years later for a murder linked to a local gay bar where he would pick men up, brutalise them, and throw the bodies in the Hudson river, describing his sick crimes as "just for fun". Whilst he's been linked to six other murders, it was only the death of Addison Verrill that left enough evidence to convict Bateson.

Scariest of all, he was released from prison in 2004.