Trivia: The music that starts to play at the end, which has become a signature tune for the twists at the end of the "Saw" films, is titled "Hello Zepp". Though the tape Adam finds actually adresses "Hello Mr. Hindle".
Trivia: The film was originally intended to be released direct-to-video, but it got such a positive response during its first screening at the Sundance Film Festival, Lionsgate decided to release it in theaters. It paid off, as "Saw" ended up spawning a franchise and becoming one of the most financially successful horror series of all time.
Trivia: Throughout the film, there are several montages of still photos. This wasn't a style choice - the budget was so tight and the shoot was so fast, they didn't always have time to get all the shots they needed. So they used photographs taken by an on-set photographer to help pad out several scenes.
Trivia: The man who is burned to death in a Jigsaw trap was actually the ex-husband of the casting agent for the film. She apparently leapt at the chance to cast him in the role when she found out his character would be horribly burned to death. (Kinda makes you wonder what their relationship was like..).
Trivia: During the fight sequence between Zep and Adam, Leigh Whannell accidentally punched Michael Emerson.
Trivia: According to the DVD commentary, during one of the shooting days on the bathroom set, someone put pins in Cary Elwes' and Leigh Whannell's shackles to close them, but they were slightly too thick. This meant the shackles could not be undone without force, so the actors had to eat lunch on the set, chained to the wall.
Answer: Amanda was supposed to put the key around Adam's neck rather than just on his chest. If she had done so as instructed by Jigsaw, he would've been able to unlock his shackle and leave the bathroom. Adam was a voyeur, the irony being that if his key had been placed correctly around his neck, all he would've had to do would be to look around to find it. Adam's tape states, "what do voyeurs see when they look into the mirror, " so, again, it's a hint that all Adam would've had to do was look at himself. I noticed as well, Jigsaw says, "the key to that chain is in the bathtub." /IS/ in the bathtub. Not /was/. So Jigsaw probably thought Adam could still get out. He says, "so many people are ungrateful to be alive. But not you. Not anymore." So it's like, 'I have taught you this lesson, now you can go free because now you'll appreciate your life unlike you did before'.