The family that was hanged on a tree were all played by stuntmen. However, when the scene was first done, the stunt coordinator botched the preparations for the scene, resulting in one of the actors coming loose from his harness, which went up around his neck. Fortunately he was not physically harmed, and the stunt coordinator was fired on set soon after.
Writer C. Robert Cargill got the idea for the script from a nightmare he had after watching The Ring (2002).
(at around 27 mins) The 'Pool Party '66' snuff film in Sinister was extremely difficult to film according to C. Robert Cargill. The actors/actresses who played the doomed family were tied down to lawn chairs and pulled underwater in reality, and the filmmakers had to be extremely careful that nobody was harmed while filming the scene took place. Further complications occurred while filming the killer underwater; Nicholas King (Bughuul) had to wear weights and stay underwater for several seconds while he was filmed. Since the scene was filmed entirely on Super 8 film, care had to be taken to ensure that the camera was properly rolling and that the cartridge and light meter were working, otherwise the scene would have to be re-shot numerous times.
There is very little blood, almost no cursing, and no sex in this movie because the filmmakers were hoping for a PG-13 rating. However, they still got an R based on content alone.
Ethan Hawke had never seen the Super 8 snuff films prior to the date of recording Sinister. When the scene where his character watches the snuff films was ready to be recorded, the soundtrack was matched up with the films and Hawke played out his role. His reactions to the films were recorded for Sinister and used in the final film.