Jennifer Jareau

Jennifer "JJ" Jareau is a special agent who was the BAU's former liaison with police and media officials. Upon her return in Season Seven, she officially becomes a profiler while her original position has gone to Aaron Hotchner (until his departure from the BAU) and Penelope Garcia. For a time, she was the acting unit chief of the BAU, taking over as Emily Prentiss was placed on suspension, pending an investigation by Assistant Director Linda Barnes and was briefly terminated.

Background
JJ grew up in the small town of East Allegheny, Pennsylvania. She graduated from East Allegheny High School near Pittsburgh, Pennsylvania, where she was the captain of the varsity soccer team her senior year and earned an athletic scholarship to the University of Pittsburgh. She also attended Georgetown University in Washington, D.C., where she was inspired to join the FBI in her senior year after hearing a lecture made by Rossi. It is also noted in Risky Business that she had a sister who committed suicide when she was young; the sister's name was revealed to be Rosaline in In The Blood. In Season Two, it is stated that she has an eight-year-old niece. She is a fully qualified federal agent but stated in Season Two that she does not want to become a profiler, even though she later took training to become one.

Even though she wasn't a profiler for the first six seasons, she often participated in the profiling process with other members of the BAU.

Season One
Being the BAU's media/police liaison, JJ has spoken to the press many times in an effort to get the media to indirectly assist in investigations and served as the first point of contact for police officers requesting the BAU's assistance. She also assisted Hotch in getting information from serial killer Jacob Dawes. JJ once went on a date to a Washington Redskins game with Reid but little has come of it romantically. She also accompanied the team and local investigators to numerous crime scenes.

Season Two
During one case, she and Reid split up at the home of the unsub and she accidentally stumbled upon a barn full of dogs who were known to eat human flesh, while Reid was abducted. Though she survived by shooting them all, the event left her with brief psychological scars; at one point while washing her hands, she hallucinated that one of the dogs was behind her, and almost shot Prentiss. She seems to have recovered in subsequent episodes, though she later told Reid at another crime scene that "no matter what happen[ed], [they weren't] going to split up".

In the episode "North Mammon", after playing a key role in the case, she responds to Hotch's question about if she ever thought about becoming a profiler by saying that she likes being the voice on the end of the phone that the detective or relatives of victims can talk to.

In the episode Jones, she meets Detective William LaMontagne, Jr. It is obvious that they are attracted to each other and at the end of the episode she gives him her number. Nothing appeared to have come of it until In Heat when she finally showed him affection in front of the team. However, they had known about the relationship from the beginning.

Season Three
In the episode Penelope, JJ shot Jason Clark Battle in front of FBI agents. The incident appeared to have little effect on her.

In Heat revealed that she and William had been dating since Jones without her telling the rest of the team (although they had figured it out long earlier). It was revealed to the viewers in The Crossing that JJ was pregnant and that New Orleans Detective William LaMontagne Jr is the father.

Season Four
JJ continued working during her pregnancy until Memoriam when she went into labor. She then went on maternity leave, her position being temporarily filled by Jordan Todd until she returned in Cold Comfort.

Season Five
In the episode 100, JJ picks up medicine for Henry with Will while searching pharmacies frequented by George Foyet.

In the episode Risky Business, JJ reveals the story of her sister Rosaline's suicide to Hotch, and then consoles him about his recent loss of his ex-wife Haley.

Season Six
When the identity of Billy Flynn is discovered by the team during his killing spree through Los Angeles, JJ is forced to act as a hostage negotiator, communicating with Flynn over the radio under Hotch's direction. JJ's speech deeply affects Flynn, who decides to release his young captive, Ellie Spicer, and commit suicide by taking a couple hostage, forcing Morgan to shoot him by threatening them.

Sometime after the Flynn case, it is revealed the Pentagon had offered JJ the position of a liaison for the Department of Defense, something she kept hidden from the team. Despite refusing the promotion twice, JJ, after a missing persons case in Maryland, is forced to take the position because of Strauss' authority, with Hotch being unable to do anything for her. At least a week later, Garcia is shown taking JJ's nameplate off the door of her old office.

JJ became part of the BAU-led interagency task force to capture Ian Doyle and briefly became a part of her old team. In the end, she is apparently one of the few people aware that Prentiss' death was faked and is last seen handing her passports and bank account information in Paris, wishing her luck.

Sometime later, she presumably takes advantage of Strauss's temporary absence from the BAU as well as the FBI's budget cuts to meet up with Rossi and tell him she's "coming back".

Season Seven
In this season, JJ officially rejoins the team, having received the training to become a full-time profiler and field agent, instead of returning to the Media Liaison rank, which now presently goes to Garcia and Hotch, who divide the position between them.

When the team captures Ian Doyle and his son is abducted, JJ and Hotch realize that they cannot get information from Doyle without Prentiss. She is flown in as Hotch tells the rest of the team that she is alive. The team realise that Declan's mother Chloe Donaghy, is behind the kidnapping, and they manage to save Declan, though Doyle and Chloe are both killed in the process. Following this, JJ and the rest of the team were placed under investigation, though Prentiss managed to clear them.

Reid later began to avoid JJ and Prentiss as he was angry with them for not telling him she was alive. He reveals that he went to JJ's house for ten weeks after Prentiss 'died', crying, and also revealed that he had thought about taking dilaudid again. Prentiss later talked to him, and he forgave her and JJ.

When an armed unsub takes a hostage and JJ confronts him alone, she convinces him to lower his weapon. However, when JJ tries to arrest him, the unsub fights back and attempts to stab her. She instantly displays adept fighting skills, which she uses to subdue the unsub. At the end of the episode, it is revealed that Morgan specifically taught her these skills, which were part of her training. When Will becomes a hostage to a group of murderous bank robbers, JJ becomes heavily distraught. The situation becomes even more dire when it turns out that Will unintentionally and indirectly gave away his and JJ's address, leaving Henry vulnerable as the unsubs had now gone on the run with Will as a captive. She and Rossi race to their house and she gets into a fight with one of the unsubs when she tries to kill Henry. The unsub nearly shoots her with her gun, but JJ is able to unload it before she can pull the trigger, right before subduing her. Will is later rescued and he proposes to her at the hospital. By the end of the episode, the two get married.

Season Eight
JJ reveals that her grandparents owned a farm in Pennsylvania and her grandmother had to do a C-section on a cow, which ends up helping with the current case. In that same episode, JJ's son Henry doesn't want to celebrate Halloween and so she convinces him to go out by saying to find out which monsters are real and which aren't. For Halloween, Henry dresses up as Reid, "his favorite profiler".

JJ reveals to Blake that her sister committed suicide. She also locates a planner and several other items belonging to Judy Morrison, which the team uses this to clear Bruce Morrison and incarcerate his daughter Sera for the crimes. In the same episode, she is held at gunpoint by Sera before Morgan and Reid rescue her.

Season Nine
It is revealed in this season that JJ knows the new BAU Section Chief Mateo Cruz (who was brought in to replace the late Erin Strauss) from her time working at the Pentagon. However, for reasons currently unknown, they keep their relationship a secret from the rest of the team. In Strange Fruit, the nature of their secrecy is partially clarified, in which it doesn't involve them having an affair.

JJ receives several calls as the BAU investigates the current case. The caller's identity or the nature of the calls has yet to be elaborated upon. At the end of the episode, she goes to a plaza with a center fountain, expecting to meet up with someone, when someone grabs her from behind and drags her away.

JJ is later held captive and tortured by her former colleague Tivon Askari, who tries to force her to reveal her the security codes that allow access to "Integrity", a database containing need-to-know information relating to the case that she worked on during her time in the State Department, called "Operation: Classified" (which specialized in tracking down Osama bin Laden), along with Cruz. She finally pretends to give in, and supplies them with a code that will trigger the alarms of the building they are in. Trying to force Cruz to do the same, Michael Hastings threatens to rape JJ, but Cruz gives in. Once the access to the case files has been obtained, Hastings leaves with several of his accomplices, while Askari is left alone with them. Askari kills a remaining accomplice, stabs Cruz in the stomach, and prepares to slash JJ's throat when Hotch and Prentiss arrive, the former killing Askari just in time. While Hotch and Prentiss attend to the severely-wounded Cruz, JJ disappears, in pursuit of Hastings. As the rest of the BAU shoot and kill Hastings's accomplices, JJ and Prentiss (who had joined her in the chase) enter the building roof, where Hastings is. Prentiss tries to apprehend him, but he retaliates and JJ is forced to intervene. Both lose their footing and fall off the roof; JJ is caught by Prentiss while Hastings falls to his death. During this episode, the real nature of JJ's work during her time at the State Department is revealed, including the danger she was in and how she was caught in a explosion, the result of which was a miscarriage of who would have been her second child with Will.

Season Ten
It is revealed JJ was still struggling to come to terms of being abducted when the one-year anniversary of the event comes up. As a result, this compromises her decisions during a case, culminating when she shoots the unsub despite the risk of triggering a gas explosion in the process.

Later, JJ announced to Reid that she was pregnant with another baby and that he could expect another godson or goddaughter.

Season Eleven
JJ is briefly seen on the phone with Hotch. They discuss JJ returning to work, and she decides that it can wait. During this phone call, she is rocking her newborn son, Michael, to sleep.

JJ's maternity ended in November 2015 and she returned to the BAU to assist them in a case.

Season Twelve
To be added

Season Thirteen
To be added