The Poughkeepsie Tapes is a found footage/mockumentary film from John Erick Dowdle (the same guy who did Quarantine and M. Night Shamalama's Devil). It's a movie that has a lot of notoriety but has never been officially released.
The Poughkeepsie Tapes is a collection of 800 tapes that get discovered after a police raid at a home in Poughkeepsie, which chronicle the crimes of a prolific and fucked up serial killer. The footage from the tapes is mixed with "testimony" and insight from law enforcement, forensics experts, media, etc. The crimes span from killing a little 8 year old girl, to home invasions, to kidnapping and killing a couple that offer the killer a ride. He manages to evade police by not having an MO or a signature. He kills in any way and manages to frame some other dude during his reign of havoc.
The main crime that's documented in the tapes is his abduction and enslavement of a 20-something year old girl named Cheryl Dempsey. His treatment, brainwashing and utter destruction of Cheryl's psyche is really the high point of this movie. The segments with Cheryl and her captivity and eventual dependency on her captor are rather creepy and disturbing.
The acting through most of the movie is kind of bland and some (not all) of it is pretty bad. The found footage itself is fairly shitty quality, like ancient footage that's been sitting at the bottom of a well type quality. But the killer and his crimes are quite clever and smart and I personally have always wondered why more serial killers don't proceed the way this guy does. It's not great but it's definitely refreshing as far as found footage flicks go and it's a movie that's worth watching.