Fitch's trap will electrocute him to death if he doesn't remove his fingers in time. The catch? The mechanism used to tear off his fingers is triggered by him clamping his teeth shut. What does electricity do? Makes the muscles tense up, including the jaw. He was going to get the fingers torn off no matter what.
Pete and several other detectives reference Marcus' former Article 8, which took place around the time when Pete murdered Charlie Emmerson. While Article 8 isn't specified, dialogue indicates that it was clearly meant to give police more unchecked powers that led to more violence. Charlie's shooting took place 15 years before the events of the movie, which you could interpret as taking place anywhere from 2019 (when it was shot) to 2021 (when it was released). Therefore, the imposition of Article 8 – which was justified because "citizens were dying" and the crime rate in the city was out of control – took place during the worst of the original Jigsaw's reign (specifically, across the first to third films, from 2004 to 2006).
Considering that the city the film takes place in is the same one as the previous films, the decline in standards of conduct which Article 8 embodies could also be, in part, a result of so many decent police officers having gotten killed, maimed, and/or discredited as collateral damage from John's schemes. The force lost so many good people to traps, treachery and scandal, the bottom-of-the-barrel cops who'd bungled or weaseled their way out of the Jigsaw investigations were all that was left to pick up the pieces, which also explains the many idiotic moments in the plot as all the smarter officers are gone.
Not to mention, one can imagine the police deciding that allowing much more abuse of power would be a Necessary Evil in order to stop other criminals that could impede the more important Jigsaw killer investigation, suspects in the investigation itself or future lawbreakers who could be just as much of a threat as John and his apprentices. It also makes sense as to why officers who refused to take part in this corruption would be so disliked, as they'd be viewed as traitors to the ideals of justice Article 8 is clearly attempting to honour (but is instead perverting).
With all this in mind, it all manages to build up a really sweet example of Irony: The Article implemented to stop Jigsaw only ended up causing the rise of another Jigsaw-like killer.
Zeke realizes at one point that the cop attacked in broad daylight is a cover for Angie being put into a trap elsewhere. Seeing as it takes Zeke himself a fair amount of time to get from one spot to the other, it implies Schenk probably has someone helping him too.
Mentioned on the film's What Could Have Been page, a trap that was removed from the movie involved Drury having to CUT HIS OWN FACE OFF. Considering how gruesome many of the later Saw traps are (and this movie alone opens with a trap that rips out Marv's tongue), the final result must have been unspeakably brutal. It's no wonder it got removed for being too violent.
New information explains that only the aftermath of it would have been shown, though.