Jason Gideon

Jason Gideon was a criminal profiler, formerly the Senior Supervisory Special Agent of the FBI's Behavioral Analysis Unit. At the beginning of Season Three, Gideon abruptly quits from the BAU for good due to emotional issues, and his position is now held by David Rossi, who has held it to this day.

Background
Gideon had reportedly suffered a nervous breakdown due to the death of six of his colleagues in a warehouse bombing before the beginning of the series. Upon his return from a six-month-long medical leave, he was given the Senior Agent position, as Hotch was confirmed as Unit Chief. Not much is known about his personal life, other than he has a son named Steven.

Season One
In the show's first episode, "Extreme Aggressor", Gideon was called back to work to help profile a killer, called "The Seattle Strangler" by the media, who abducts women and holds them prisoner before strangling them and dumping their bodies. After Gideon puts together a profile, they believe the unsub is Richard Slessman, a convicted serial rapist. When they pick up Slessman, the pieces do not all fit together, and they conclude Slessman is the "brains" of a duo. The team eventually discovers that Timothy Vogel, a prison guard that protected Slessman while he was in jail, is the actual perpetrator of the crimes. Gideon succeeds in saving Heather Woodland's life by angering Vogel to the point that he forgets about the victim and tries to kill Gideon, only to be shot by Elle.

In the episode "Won't Get Fooled Again", a copycat bomber uses the methods of serial bomber Adrian Bale (the same criminal who committed the warehouse bombing that killed his six colleagues), and Gideon has to face his past, and Bale, to find out who the bomber is and stop him. After saving the lives of more agents from a suicide bombing, Gideon was forced to make a deal with Bale to have him help them get a bomb off of an innocent man. When Gideon realizes that Bale is lying about how dismantle it, he calls his bluff, saving them all from a bomb going off. He then has the pleasure of returning Bale to prison, the burden of the six agents' deaths presumably gone, even mocking him while he was being placed in a cell by using Bale's own words ("[A]n emotional release") in a sentence; he states that he finds it an emotional release in putting away criminals like Bale.

In the episode "Plain Sight", Gideon is a major reason that the team is able to catch "The Tommy Killer", a serial rapist and killer who would glue his victims' eyes open. Gideon discovers that this serial killer is a phone technician and glues his victims eyes open because he feels invisible. He manages to confront the killer when he is about to kill another woman, persuading him that he will make him famous, causing the killer to surrender and release the hostage.

In "The Fox", Gideon was the main reason that the BAU was able to convict Karl Arnold, a.k.a. "The Fox", to the murders of five families. With no forensic evidence to link Karl to the crimes, they needed a confession in order to convict him. Gideon, knowing that Karl was obessed with keeping things in order, mixed up the pictures of the victims' bodies. This was more successful than he anticipated; Karl knew that not only were the pictures out of order but was able to identify the bodies, which only the murderer would know. With this damning evidence, the BAU was able to convict and inprison Karl.

In the episode "What Fresh Hell?", Gideon saves the life of eleven-year-old Billie Copeland, who was abducted by a pedophile. When the BAU receives information from a neighbor of a man named Donald Curtis, they find that he matches the description of the unsub, with Curtis even having the same green van and a deceased dog named Candy. Gideon forced his way into the home but finds no trace of the girl. He searches the house and still has no luck until he notices some insulin on a broom and remembers that Curtis had insulin on his jacket. Gideon realizes that Billie may be held in an attic, an assumption that was correct.

In "Riding the Lightning", the BAU travels to a prison to interview a killer couple, Jacob Dawes and Sarah Jean Mason; Jacob killed at least eighteen women, while Sarah admitted to killing her son Riley Dawes under Jacob's orders. Gideon, however, believed that Sarah was innocent and that Sarah was protecting her son from Jacob. However, even after Jacob was executed, Sarah would not tell Gideon anything. He eventually discovered that Riley was alive after finding a picture of him in one of Sarah's paintings, and found that he was adopted by another family. Even with this discovery, Gideon realized that Sarah wants her son to have a brand-new life without the knowledge that his parents were criminals, so he allows Sarah to be executed.

Season Two
After a series of emotional cases, one of which resulted in the death of his girlfriend and another which ended with the deaths of two unsubs, Gideon began feeling very emotionally distressed, to the point where he began seeing his girlfriend. The last straw was Hotch's two-week suspension, for which Gideon felt responsible. He retreated to his cabin during the suspension and left a letter for Reid, who he knew would be the one to come looking for him. When Reid arrived at the cabin, it was empty except for the letter and Gideon's badge and gun. Gideon was last seen remarking to a Nevada diner waitress that he didn't know where he was going or how he'd know when he got there, leaving the diner and subsequently driving off in his vehicle. He also mentioned that one of his reasons for resigning from the BAU for good was to regain belief in himself and happy endings.

Although Gideon no longer appears in the series, numerous characters, including Reid, have mentioned him occasionally from time to time. The latest reference to him was in the Season Eight episode Carbon Copy, where it is revealed that he was the head of the team at the time they investigated the Jack Lee Kemper case in Philadelphia, Pennsylvania, a case that proved to be the catalyst for Donnie Bidwell's killings.