Ed Warren and Lorraine Warren, who are known for involvement in The Amityville Horror case, were investigators for this case.
Author Ray Garton, who wrote In A Dark Place, has distanced himself from the claims of the Snedecker family and the Warrens. He has continually disowned the book, proclaiming it to be 100% fiction.
The movie is loosely based on the real life stories of Al and Carmen Snedeker who lived in a reportedly haunted former funeral parlor in Southington, Connecticut.
There are some authentic (i.e. not mocked up especially for the occasion) photos purporting to show ectoplasm in this movie. However, though they were seized upon as authentic at the time; most people now acknowledge that what is shown is regurgitated cheesecloth. (Mary Roach's "Spook")