The Conjuring: The Devil Made Me Do It centers on the notorious story of Arne Cheyenne Johnson, a man who was convicted of killing his landlord in the early 1980s and in court was the first known person in United States history to claim that he was innocent because he was possessed when the murder was committed. At the time, Arne was dating a young woman named Debbie Glatzel, and prior to the crime he was present at an exorcism for Debbie’s brother, David – which is when, he claims, the evil spirit entered his body. Ed and Lorraine Warren were both a part of David’s church-sanctioned demon removal, which is the scene that starts the new movie.
Article source: https://www.cinemablend.com/news/2567140/conjuring-3-honestly-darkest-warren-case-yet-director-michael-chaves