The film focuses primarily on the events that led up to Detective Mark Hoffman becoming an apprentice of the Jigsaw Killer, as well as his efforts to prevent anyone else from learning his secret.
Convicted murderer Seth Baxter wakes up chained to a table beneath a pendulum blade. A videotape informs him that he can release himself by crushing his hands between two presses. He does so, but the blade still swings down and cuts him in half as someone watches through a hole in the wall.
In the meatpacking plant, FBI Agent Peter Strahm guns down Jeff Denlon and is locked in the sickroom. He discovers a hidden exit and a microcassette recorder, which urges him to stay in the sickroom, but he ignores it and is attacked in the tunnel by a pig-masked figure. He wakes up with his head sealed in a box which quickly fills with water, but survives by performing a tracheotomy with his pen. Outside, Detective Mark Hoffman delivers Corbett Denlon to the police and claims they are the only survivors, but is shocked when Strahm is brought out alive as well.
During a press conference, Hoffman is promoted to detective lieutenant and credited with closing the case. He finds a note in his office that reads "I know who you are" and learns of Lindsey Perez's death while taking Strahm's phone. At the hospital, Strahm tells Hoffman that Perez's last words were his name, and questions how he escaped the plant. Strahm is also visited by his boss, Dan Erickson, who puts him on medical leave. Suspicious of Hoffman and determined to piece together his involvement with Jigsaw, Strahm takes case files of past victims and begins researching on his own.
In an underground room, five people awaken with collars connected to mounted blades locked around their necks, the keys to which are in glass boxes across the room. A videotape claims that all five of them are connected and implores them to "do the opposite" of their instincts throughout the game. Mallick, an arsonist, activates the timer and everyone reaches their keys except Ashley, a former fire inspector, who is decapitated when the collars retract. In the next room, they learn that the overhead jars contain keys to three bomb shelters. Charles, an investigative journalist, strikes Mallick and begins smashing the jars one by one. Brit, a real estate vice president, and Luba, a city planner, each find a key and Charles takes Mallick's, only to be struck by Luba and left to die when the bomb detonates. In the third room, five short cables must be connected to a full bathtub to unlock the door. Luba attacks Mallick to use his body to close the circuits, but Brit stabs her and they use hers instead. In the fourth room, they find a machine fitted with circular saws and a beaker requiring ten pints of blood to open the door. Mallick notes the five armholes and they realize that all five of them were meant to work together to survive the game. Brit also works out their connection: they were all involved with a building fire that killed eight people. With no other options, they saw their arms to provide the blood.
Meanwhile, Strahm learns that Baxter killed Hoffman's sister, and was released from prison on a technicality. As revenge, Hoffman later abducted and killed Baxter, using the pendulum trap to frame Jigsaw. He was later abducted by John Kramer, who blackmailed Hoffman into working with him. They set up most of the games together, with Hoffman planting Lawrence Gordon's penlight and providing the police files for the nerve gas house victims. Strahm realizes in the end that everyone was meant to die in the plant except for Corbett and Hoffman, who would become a hero. His activities soon draw Erickson's worry, which is further fueled when Jill, who received a box and a videotape from Kramer's will, approaches Erickson and claims Strahm is stalking her. After Hoffman calls Erickson to tell him about Strahm's theory of a second accomplice, Erickson puts a tracker on Strahm's phone.
Erickson follows the tracker to the observation room and finds the phone and his own personnel file, planted by Hoffman. He also finds Brit, who has managed to crawl from the fourth room after Mallick passed out from blood loss. Erickson calls for medical attention for the victims, and puts out an all-points bulletin on Strahm, who follows Hoffman to the renovated nerve gas house, and finds an underground room containing a clear box filled with broken glass. Hoffman's tape urges Strahm to enter the box, but he stops it short and ambushes Hoffman. After a brief struggle he seals Hoffman in the box, which seals the room's exit. Hoffman indicates the tape, which warns Strahm that if he does not enter the box he will disappear and inherit the Jigsaw legacy. The box is safely lowered into the floor as the walls close in on Strahm, who unsuccessfully attempts to escape through the ceiling grid, and is crushed to death.
Saw V was written by Patrick Melton and Marcus Dunstan, and the film went into production after Christmas 2007. Principal photography took place from March 17, 2008 to April 28, 2008 in Toronto. By mid-July 2008, there had been three photos released of David Hackl at the set of Saw V. The first trailer, depicting Agent Strahm's box trap, was released at Comic-Con 08 as a short clip and the trailer was also shown before The X-Files: I Want to Believe. The website opened on August 6, 2008. On September 17, 2008, a new clip was available on the Saw V website, depicting the Pendulum Trap.
The film was released in Australia on October 23, 2008, in North America and the United Kingdom on October 24, 2008, and in New Zealand on October 30, 2008.
In its opening weekend, Saw V grossed $30,053,954 in 3,060 theaters in the United States and Canada, ranking number two at the box office behind High School Musical 3: Senior Year. It grossed $56,746,769 in the United States and Canada, and an additional $57,117,290 in other markets, for a worldwide total of $113,864,059. This was the second film in the series to not be number one at the box office, the first was the first film. It is Lionsgate's tenth highest-grossing film in the United States and Canada.
The film received generally negative reviews from critics. The review aggregator Rotten Tomatoes reported that 12% of critics gave the film positive reviews, making it the second poorest-reviewed film in the series, losing to the most recent Saw 3D. The Rotten Tomatoes consensus states "If its plot were as interesting as its torture devices, or its violence less painful than its performances, perhaps Saw V might not feel like it was running on fumes." Metacritic reported the film had an average score of 20 out of 100, based on 13 reviews.
Elizabeth Weizman of the New York Daily News believed that the lack of Tobin Bell's Jigsaw character hurt the film: "Bell's deliciously twisted madman was the lifeline of this series, and without him, we're left watching a routine horror flick that might as well have gone straight to DVD. The series began with two major assets that set it apart: the concept of a brilliantly righteous executioner, and the actor who played him. Now, aside from Bell's brief, intermittent cameos, it has neither. So where the original Saw was diabolical fun, this fifth installment is as bloodless as the most unfortunate of Jigsaw's victims." Sam Adams of the Los Angeles Times wrote that "The virtues of the individual films are almost beside the point, since it's hard to imagine why anyone would want to pick up the thread at this late date, but Saw V is a particularly dull and discombobulated affair, shot and acted with all the flair of a basic-cable procedural".
Some reviews were positive, however. The British website Digital Spy rated it 3/5 stars and commended the film for its "solid acting, slick direction and suitably filthy cinematography too", while also stating it will "make far more sense to those familiar with the previous installments". IGN awarded the film with 3 out of 5 stars stating that the film ties up most of the loose ends of the previous 4 installments while also having a more straightforward and less complicated storyline. They also praised the traps for being the most inventive and best that the Saw franchise has had to offer.
During an interview at the 2008 Scream Awards, Hackl claimed that his director's cut of Saw V (released on DVD January 20, 2009), would run approximately 14 minutes longer than the theatrical cut. Hackl also stated that a number of scenes in the film would be re-ordered and arranged differently than in the theatrical cut. However, only a few changes were made and the extra footage was never released, running only four minutes longer than the theatrical version.
A collector's edition is available with exclusive packaging. It features sound effects, a collector's booklet, and a spinning "saw blade". The features on the DVD itself are the same as the standard Unrated Director's Cut.
The soundtrack was released on October 21, 2008 by Artists' Addiction Records.