Harrowing clip shows real-life murderer acting on the set of The Exorcist

Horror films don’t get much scarier than The Exorcist which has left people too scared to sleep for decades.

However, if one thing could make the 1973 tale about the demonic possession of a young girl even more frightening, then it is the fact that one of the scenes features a real-life suspected serial killer.

The William Friedkin-directed film tells the story of Regan (Linda Blair), a 12-year-old who is possessed by the devil and her mother’s attempts to rescue her through an exorcism performed by two Catholic priests.

In one scene, Regan is taken to hospital to undergo tests, during which a catheter is inserted into her neck through an artery and Regan grimaces as blood spurts from her neck.

Although that scene alone would be enough to make anyone grimace, it turns out that one of the hospital technicians is played by Paul Bateson, convicted in 1979 of the murder of film industry journalist, Addison Verrill. Bateson is also suspected of several other murders within the gay community of Manhattan, New York in the 70s.

Although he was convicted for the 1979 murder of Verrill, Manhattan police had been suspicious of Bateson for some time following the deaths of several gay men.

Verrill was found beaten and stabbed to death in his own flat, after which the journalist's friend - fellow writer Arthur Bell - urged the killer to come forward via an article in the U.S. news weekly, The Village Voice.

Warner Bros.

A video filmed behind the scenes on set of The Exorcist, which was filmed in the summer of 1972, shows Bateson standing alongside Blair who is in a hospital bed.

Bateson helps to wheel the hospital bed into the room and stands beside it as Blair laughs at the camera in between takes while drinking from a cup.

Bateson’s appearance in The Exorcism seems to fly under the radar even after a character based on him is featured in the cult Netflix crime drama Mindhunter.

In case you haven't seen it, the show is based on a true crime book about the FBI’s ‘Elite Serial Crime Unit’ who came up with a psychological profile to help catch serial killers.

Warner Bros.

Bateson was originally a radiographer and he came to the attention of Friedkin when the director visited the New York University Medical Centre, where Bateson worked, to undertake some research.

Friedkin was by his work and invited Bateson to work as an extra on The Exorcist, and it is his character who calmly explains to Regan what will happen to her during the procedure.

Bateson was released in 2003 after being granted parole. However, a social security record shows a Patrick F. Bateson with the same birthdate passing away in 2012, with the murders of the other men in 1970s Manhattan still no nearer to being solved.