Dunstan has written the screenplays for Feast, Feast 2: Sloppy Seconds, Feast III: The Happy Finish, The Collector, Saw IV, Saw V, Saw VI, and Saw 3D. He is also in pre-production and post-production for several of his other screenplays. In addition to writing the screenplay for The Collector, he directed the film. He also directed the sequel to The Collector, titled The Collection. The film, produced by Liddell Entertainment and Fortress Features, was released in 2012.