Just research all the ones that made it into books or movies. Like The Amityville Horror which was an intentional hoax. Or the Exorcist and good luck finding out what that was actually based on because I've heard three separate explanations with the most likely being a second hand tall tale some Georgetown Jesuit told Blatty when they would get together for drinks. Without a lot of information, he made most of it up, but it's still a great movie. It just never happened. That doesn't make the story worse, but when a movie like THE CONJURING claims to be true and the actual people are still alive AND it implies that the people hanged for witchcraft in Salem really were witches, that's a bit of a problem.
The movies themselves are obviously completely fictional - like any movie based on a true story - but even the stories they are based on end up full of holes with many of the "witnesses" actually dismissing or explaining the ghosts and demons with natural causes or proving that the whole thing was either a hoax or mundane events were mythologized long after the fact.
Hardly anyone would really trust one of the many psychics who set up shop along the street or (illegally) in residential houses and most only go to them as a lark - like going to a haunted house on halloween. However, In many of these "true" stories, those same people are considered expert witnesses. We've all seen that same scene in every haunted house movie where they walk in the front door and then look like they had cold water thrown in their faces, but that's just the movies. In real life, it's a scam.
The paranormal is a business - specifically, it's show business, for the most part, and a lot of what passes as paranormal science today was debunked when it was called spiritualism in the 19th and early 20th centuries.