Law Abiding Citizen

Clyde Shelton (Gerard Butler), a Philadelphia engineer, witnesses the rape and murder of both his wife and five-year old daughter at the hands of two burglars who break in his house: Clarence J. Darby (Christian Stolte) and accomplice Rupert Ames (Josh Stewart), leaving Shelton emotionally scarred. He is told by career-minded prosecutor Nick Rice (Jamie Foxx) that the case was compromised by a bungled forensic investigation and Shelton's testimony cannot incriminate either man because he blacked out during the incident. Rice, interested in maintaining his 96% conviction rate, makes a secret deal with Darby: in return for pleading guilty to third-degree murder, he will provide testimony that will send Ames to death row for what is, essentially, a robbery charge. Shelton is left feeling betrayed.Ten years later. Ames is executed via lethal injection. Due to an alteration in the chemicals, he dies in agonizing pain. Initial evidence leads to Darby, who is alerted to approaching police by a mysterious caller who tells him where a pistol he can use to his advantage is. The caller tells him if he wants to escape the police, he will come to where he is. At the meeting place, Darby realizes that the caller and his savior is none other then Shelton. Darby tries to shoot him with the pistol, only to be discover it is a trick gun, injecting him with tetrodotoxin, paralyzing him, but leaving him fully conscious. After restraining him and making preparations to ensure his prolonged awareness, Shelton slowly tortures and dismembers Darby, saying the words Darby told him 10 years before: "You can't fight fate." It is later revealed that Darby was found in 25 pieces, and after an investigation, Rice and his team suspect Shelton.The next day, a local SWAT unit bursts into Shelton's house to find him waiting for them, and he doesn't resist arrest. In an interrogation cell at the jail, Rice covertly congratulates him for removing Darby from society, then asks for a confession. By all appearances co-operative, Shelton offers a full confession in exchange for a deluxe mattress in his cell; Rice reluctantly agrees. At his hearing, Shelton opposes a motion to deny himself bail, citing obscure legal precedents. Judge Laura Burch (Annie Corley), who also presided at Ames' trial, agrees, but Shelton launches into a tirade against the court's preference for legal technicalities over justice. He is removed for contempt of court.After receiving his mattress and delivering the confession, in which he confesses not only to killing Darby but also to having altered the lethal injection chemical that made Ames' death agonizing, Shelton bargains to give the location of Bill Reynolds (Richard Portnow), Darby's attorney, who was reported missing three days before, in return for an expensive steak dinner from Del Frisco's to be delivered at precisely 1 p.m., along with his iPod. Warden Inger (Gregory Itzin) demands multiple precautions, resulting in the food arriving at Shelton's cell eight minutes late. Rice and Detective Dunnigan (Colm Meaney) find Reynolds buried alive and only minutes dead, with Inger's delay causing him to suffocate, his oxygen tank having been set to shut down at 1:15. Dunnigan explains that because Shelton received his lunch at 1:08, they were 7 minutes late instead of getting to Reynolds in time to save him.Shelton and his cellmate, who had threatened to hurt him if he refused to share, eat the steak dinner together. Shelton then murders him by using the steak T-bone as a knife. He is sent to solitary confinement. Rice's assistant, Sarah Lowell (Leslie Bibb), finds evidence of contract payments to Shelton from the Department of Defense, so the head D.A. Jonas Cantrell (Bruce McGill) takes Rice to meet a CIA operative Bray (Michael Kelly) who worked with Shelton. They learn Shelton was once a CIA "brain" working in a black ops think tank on unconventional methods of killing targets. Bray tells them to assume that he can see them and hear them at all times, he is always watching. He also warns them that he's only in jail because he wants to be in jail, and that each thing he does has a deeper meaning. When Rice asks how they should deal with Shelton, Bray advises them to "walk into his cell and put a bullet in his head", otherwise they cannot stop him. As he leaves he says, "If Clyde wants you dead... you're dead".Rice and Cantrell convince Judge Burch to violate Shelton's civil rights and restrict his visting privileges. Minutes later, Judge Burch answers a cell phone which explodes, killing her instantly. At the prison, Rice confronts Shelton, who says these killings are not about revenge but about the failure of the justice system. Unless he is released with all charges dropped by 6:00 a.m . tomorrow, he will kill "everyone."Members of the DA's staff congregate until 6:00 a.m.. They are sent home, but bombs planted underneath their cars go off and kill those inside, including Sarah. Shelton was still incarcerated, so Rice assumes he is using an accomplice outside to help.At Sarah's funeral, an unseen man wearing black clothing powers up a remote controled drone armed with a rocket launcher and a .50 caliber machine gun. The kills Cantrell as he is riding in a SUV with security detail. Rice is appointed acting District Attorney by the uptight mayor (Viola Davis) whom is angry at Rice for his failure to protect everyone.While looking for evidence that Shelton may have accomplices working for him, Rice receives information that points to Shelton owning a small disused garage next to the prison. Rice and Detective Dunnigan arrive at the garage and while looking around, they find a tunnel system leading to all the solitary confinement cells, along with a large supply of armaments. Apparently over the past 10 years, Shelton had dug the tunnel system from his garage to the prison and when it was finished, he deliberately had himself arrested and sent to solitary confinment in order to sneak out of the prison to carry out his killings undetected and all by himself, and then sneak back into his cell the very next day. Dunnigan opens a small hole and finds that it leads to Shelton's cell, which is empty.Disguised as a janitor, Shelton plants a cell phone activated napalm bomb in City Hall, planning to kill the mayor and anyone attending her meeting. Rice, Dunnigan and Detective Garza (Michael Irby) infiltrate the 5th floor and find the bomb directly under the 6th floor, where the mayor is situated at a security meeting. Garza attempts to disarm the bomb, but is unsuccessful and warns them to leave it alone. The three men then decide not to tell the mayor what is going on, as Shelton will be watching and will detonate the bomb with any sign of detection. They then decide what to do with the bomb.Upon returning to his cell through the underground tunnel, Shelton discovers Rice there waiting for him. Shelton offers one last deal, but Rice says that he no longer makes deals with murderers, which Shelton appreciates. Rice says to Shelton that if he detonates the bomb, "It's a decision you'll have to live with for the rest of your life." With his wife and daughter long dead and feeling that he has nothing to live for anymore, Shelton decides to detonate the napalm bomb anyway, but as Rice exits and locks the cell, he calmly says ," Like I said, it's a decision you'll have to live with for the rest of your life, which I think now is about 25 seconds". He then begins to flee the building. At the same time, Detective Dunnigan seals the hatch in the back of the cell to ensure Shelton doesn't escape. Shelton realizes that the bomb was placed under his cot, but merely smiles and stares thoughtfully at a bracelet his daughter had made for him which says "DADDY". The cell explodes, with the last shot of Shelton alive being of him looking up with an almost satisfied expression.In the final scene, Rice is seen attending his own daughter's music recital, an event he had previously put off due to work. He rises with the crowd as they cheer her on after the performance.

Question: Who altered Ames' lethal injection?
Answer: Shelton