In the Season 13 episode "Annihilator" Barnes volunteers the BAU team to investigate a murder in St. Louis not because of any innate desire to help, but because she believes the case will be easy to solve and provide the team with good optics. Despite not being a profiler herself, she invites herself along and begins assigning BAU members to specific avenues of investigation, despite having named JJ as the acting lead in the field. As the case progresses, she becomes convinced that a man named Larry is the killer, and when Larry is found dead of an apparent suicide, she's convinced the case is closed. Tara (Aisha Tyler) and JJ quickly work out the suicide note is faked, however.
The team managed to find the killer, who is cornered at an airport and threatening suicide unless a witness they have in custody (a woman the killer is obsessed with) is brought to him. Despite the fact that it's obvious the killer is planning something, Barnes brings the woman to the scene in an attempt to pacify the killer, who instead attempts to shoot the civilian. The civilian survives, thanks to a bulletproof vest, but his attack forces the BAU team to have to put the killer down rather than arrest him.
