Understandably Scott Patterson was a little apprehensive about sticking his head in a sealed box that would fill with water. The trap was tested beforehand and didn't go terribly well, which only added to his concern. Ultimately, the actor stepped up and did the scene himself without resorting to a stuntman. The trick to the stunt is that the walls of the box were slid open by stagehands, draining the trap as soon as Patterson signaled with his hands. Several takes were required however to capture the scene as Patterson found himself uncomfortable at various points during the shooting of this scene.
When director David Hackl screened the film for composer Charlie Clouser, the musician had to turn his back to the footage of the final ordeal for the last two contestants as he couldn't stomach what he was seeing.
The original screenplay called for the characters played by Meagan Good and Julie Benz to go through most of their ordeal wearing just their undergarments. The production team decided against this when they realized how committed and serious the two actresses were about their roles.
During the production of the film there were widespread rumors that actor Scott Patterson was unavailable for filming. As a result his appearance would be relegated to a cameo. The hype for the film included trailers and posters for the Glass Box trap which opens the film. The anticipation was that Agent Strahm would die at an early stage. This increased the suspense of the audience until the release of the film whether Agent Strahm would survive the opening trap and added to the mystery of who would be the leading character in Saw V.
The opening pendulum trap was a real working model. However, for the times when the actor was underneath it, the metal blade was replaced with a foam one. Likewise, the hand-crushers were foam too except for the close-up shots where they looked too fake. Real heavy duty material was used then with a prosthetic hand inserted.
(at around 11 mins) The scene where Hoffman leaves the Gideon plant with Corbett and says "nobody made it" was filmed for, and edited out of, Saw IV (2007). Behind-the-scenes footage of this scene appears in Darren's Video Diary on the DVD and Blu-ray of Saw IV.
at around 15 mins) Although the body of Detective Tapp from the first Saw film was never recovered and is never visible in any of the sequels, his picture among the other deceased police officers at least establishes his death. Although there are not any details about how his body disappeared from the corridor outside the bathroom (in contrast to other bodies that stayed locked inside the bathroom such as Zepp) this picture proves that Tapp's death is known to the police and that his remains were found. The first Saw video game (Saw (2009)) elaborates on Tapp's fate after the events of the first film.
at around 1h 26 mins) This features one of the rare occasions when a crushing room actually crushes someone. Generally characters will manage to escape from such a scenario, for instance, in Star Wars: Episode IV - A New Hope (1977).
Actor Scott Patterson did not know the film's ending. The SFX team started doing casts of Patterson's arms (That are later used to simulate his bones breaking in the crushing trap) and he asked what they were for. Patterson laughingly said that the SFX technician, surprised he didn't know, told him that they were killing his character off at the end.
Body Count: 6. (Including Seth Baxter and Angelina Hoffman, whose deaths are shown in flashbacks. Mallick and Brit's fates are unknown at the end of the film, however, they are revealed to have survived in Saw 3D: The Final Chapter (2010).)