was the exorcist based on a true story?

best answer
The Exorcist true story is based on the experience of Roland Doe. In March 1949 newspapers reported that a 14-year-old boy known as “Robbie” or “Roland Doe” was possessed by something sinister and that The Exorcists priests performed an exorcism on him. The boy raised in a German Lutheran family was no stranger to the paranormal things in life.