The Exorcist was loosely based on true events that were reported in Washington, DC newspapers in 1949.
The story began in Maryland on the evening of January 15, 1949, when 14-year-old "John Hoffman" and his grandmother heard strange scratching and dripping noises in their house. No explanation could be found for the noises, which stopped after ten days, only to be replaced by mysterious footsteps and drumbeats.
After John's Aunt Dorothy suddenly died, the poltergeist-like phenomena increased - with John's mattress shaking violently, food flying through the air and furniture falling over. John and his parents tried to communicate with the poltergeist, which at the time claimed to be the spirit of Aunt Dorothy.TALKING SKIN
Then, in late February, livid red marks emerged on John's skin, taking the shape of actual words. After neither physicians nor psychiatrists could find anything wrong with John, his parents, although Lutheran, consulted a Roman Catholic priest. His recommendations of prayers and holy water only seemed to aggravate John's condition.
John's mother took him to St. Louis, hoping things would calm down. But the manifestations intensified. "Father Lawrence," a Jesuit priest, came to visit John in St. Louis, saying prayers over him and pinning two crucifixes under his pillow.
After he left, one crucifix propelled itself across the room and the other moved to the foot of the bed as the bed shook violently.BEGIN THE EXORCISM
On March 16, the Archbishop of St. Louis gave Father Lawrence permission to begin the formal rite of exorcism.
During the first night of the ritual, marks appeared on John's skin 30 times -- including the word "Hell" and a portrait of a Satanic visage. The 45-minute ritual was performed several times a night over the next week. John's responses became increasingly rabid, including screaming torrents of profanity and foreign words, violent seizures and uncontrolled urinating. With the parents' permission, John was converted to Catholicism. But his responses to the rituals only became worse. The disturbances suddenly stopped on March 26. Father Lawrence believed John's possession was over.
"I AM ALWAYS IN HIM"
However, they began again on March 31, with John's behavior during the rituals getting even more violent. "I am always in him," the demon said through John's lips.
After more days of no progress, Father Lawrence read about an 1870 case of possession that provided a key to exorcising the demon.
On the night of April 18, he forced John to wear a chain of religious medals and hold a crucifix in his hand during the exorcism ritual. When Father Lawrence commanded the demon to declare itself, John exploded in a violent spasm of amazing strength, needing five men to hold him down.
At 11 p.m., John suddenly interrupted the ritual by shouting, "Satan! I am St. Michael. I command you, Satan, to leave his body now!" After then enduring the most violent spasms yet, John uttered, "He is gone" and suddenly returned to normal, breaking into a smile.
John grew up to live a normal, happy life, with no recollection of his "possession."
William Peter Blatty, then a student at Georgetown University, read about John's story in the newspapers. The story stuck with him and 20 years later he fictionalized it to create "The Exorcist."