Documentary film is often claimed to be the most "truthful" form of the cinematic medium. People turn to this genre to find facts, make discoveries, and learn something new. It's a genre that's been around from the very beginning too - with Workers Leaving the Lumiere Factory considered by many as the first real documentary ever made, along with its known reputation as one of the first ever cinematic productions. Indeed, documentary is a genre that has spawned some of cinema's greatest achievements. A variety of wonderful films have employed the form, ranging from Michael Apted's Up! series, to Steve James' Hoop Dreams. Other directors such as Michael Moore and Morgan Spurlock have used the documentary method to help turn heads to troubling societal issues such as health care and fast food, whereas the likes of Woody Allen have used the form to provide a false sense of authenticity to otherwise unbelievable subject-matter (Zelig, Take the Money and Run). Here, we're going to take a look at the documentary films that use their strong sense of realism to send shivers down the spines of audiences. These films don't simply scare through use of red herrings, flash-cuts and loud noises. They use cold facts and real footage to wriggle under the skin of viewers and give them goosebumps. Using subject-matter that often involve disputes, deception, and death - below are some of the most truly chilling documentaries ever made.