History Film / SawIV

* CreepySouvenir: Ivan, a serial rapist, keeps Polaroids of his rapes stashed away at his motel, and it is heavily implied that he masturbates to them regularly.

** Averted by Strahm and Perez. They're both scripted as highly intelligent FBI agents, and despite Perez being his junior, Strahm treats her with complete respect, even [[spoiler:breaking down in tears and talking to her mother on phone when she's critically wounded in his sight]]. While both agents eventually get overwhelmed by the pressure of the situation, [[spoiler: Strahm figures out that the main action is taking place at the Gideon Meatpacking Plant (though not without recklessly killing Jeff once he gets there)]].

* PrecisionFStrike: While his test subjects swear heavily, Jigsaw barely uses any foul language, and this is the first time he's seen using it. [[spoiler:In the flashbacks where he's reeling from the death of his son Gideon, John says "Get the fuck out of here!" to a guy who was asking him if he was sure about cutting off his funding for Jill's drug rehabilitation clinic.]]

* POVSequel: [[spoiler:The climax reveals that most of the film's events have been taking place at the same time as ''Saw III'', but in different locations. This is only explicitly shown when Strahm runs into Jeff, the protagonist of ''III'', in the Gideon Meatpacking Plant, and finds the corpses of the third film. Rigg, despite also entering the plant, doesn't witness anything related to the plot of ''III'', with the exception of Kerry's corpse (which was outside the plant).]]

** Somewhat played straight. Rigg is essentially "recruited" to stand in for Jigsaw for his tests. Eric is psychologically broken, to the point where he tries to kill himself in his new trap, and [[spoiler: the only other key cop from the local precinct we've met, Hoffman, is also in a trap, and ends up being Jigsaw's other apprentice.]]
** Somewhat subverted by Strahm and Perez. They're both scripted as highly intelligent agents, and despite Perez being his junior, he treats her with complete respect, [[spoiler: even breaking down in tears when she's critically wounded.]] Both Strahm and Perez eventually start getting overwhelmed by the situation, [[spoiler: though Strahm figures out that the main action is taking place at the Gideon Meatpacking Plant.]]

* RecklessGunUsage: [[spoiler:Art points a revolver at a restrained Hoffman to calm an also-restrained Eric Matthews down... while keeping his finger on the trigger.]]

* PoliceAreUseless: Somewhat played straight. Rigg is essentially "recruited" to stand in for Jigsaw for his tests. Eric is psychologically broken, to the point where he tries to kill himself in his new trap, and [[spoiler: the only other key cop from the local precinct we've met, Hoffman, is also in a trap, and ends up being Jigsaw's other apprentice.]]
** Somewhat subverted by Strahm and Perez. They're both scripted as highly intelligent agents, and despite Perez being his junior, he treats her with complete respect, [[spoiler: even breaking down in tears when she's critically wounded.]] Both Strahm and Perez eventually start getting overwhelmed by the situation, [[spoiler: though Strahm figures out that the main action is taking place at the Gideon Meat Packing Plant in the end.]]

* MemoryTrigger: After forcing Ivan into the Bedroom Trap at the motel, Rigg comes across a letter that reads "Become the teacher and save a life. Go back where it all began." This triggers a flashback of him at an elementary school in his early police career as a regular uniformed cop; in the present, said school (confirmed by [[invoked]]WordOfGod to be the abandoned one previously seen in ''Film/SawIII'') is the building that Rigg subsequently goes to and where he finds the place for his next test.

* MemoryTrigger: After forcing Ivan into the Bedroom Trap at the motel, Rigg comes across a letter that reads "Become the teacher and save a life. Go back where it all began." This triggers a flashback of him at a school in his early police career as a regular uniformed cop; said school (confirmed by [[invoked]]WordOfGod to be the abandoned one previously seen in ''Film/SawIII'') is the building that Rigg subsequently goes to and where he finds the place for his next test.

** During Jigsaw's autopsy, his brain is easily removed from the skull, apparently with no connection to the brain stem or spinal cord. In reality, a ton of dissection is needed to remove the brain.

** Brenda's trap wouldn't scalp her in real life; her hair would rip and tear before her scalp would. Hair might be strong, but it's not that strong.

*** Speaking of the autopsy, John somehow managed to swallow a tape coated in wax, which also worked perfectly after it was removed from his corpse.

** John somehow managed to swallow a tape coated in wax, which also worked perfectly after it was removed during his autopsy.

* AntiHero: One of Rigg's fatal flaws. To start, he has a temperamental and focused personality, which stems from such situations, where he acted aggressive, and on some occasions, even turned violent, which brought him into conflict with the Internal Affairs Department. Despite this, Rigg is loyal to both his friends and his department, is extremely dedicated to his work and had a strong sense of justice. However, his quest to save and protect everyone turned into an obsession, [[spoiler:which proves to be his undoing]]. For what Jigsaw meant his trial to be about, see UnwantedAssistance below.

* FondMemoriesThatCouldHaveBeen: In the hindsight from ''Film/SawII'' (see the trope's entry in that movie's page for context), Eric and Daniel's father–son relationship ultimately plays the trope painfully straight, even though Daniel isn't present in the film, as [[spoiler:Eric ends up dying before he could get out of the confinement that John and Hoffman have had kept him in for months and meet Daniel once again]].

* MistakenForRelated: A single-receptor variant involving multiple relatives. In his last meeting at the police station with Strahm and Perez before he's abducted, Hoffman shows up carrying a teddy bear. Looking at the teddy bear, Perez assumes that Hoffman has a wife and a child, which he denies as being a "short story". [[spoiler:The teddy bear is actually a hint at what's revealed at the end of the movie, since it's the same one that Corbett Denlon had in ''Film/SawIII''.]]

->''"I promise that my work will continue. You think it's over, just because I'm dead? It's not over. [[MyDeathIsJustTheBeginning The games have just begun.]]"''

->''"I promise... that my work will continue. You think it's over, just because I'm dead? It's not over. [[MyDeathIsJustTheBeginning The games have just begun.]]"''