|Full Name||Katherine Brennan|
|Affiliation||Chicago Police Department (former)|
|Occupation||Police Officer (former)|
|Rank||Dep. Superintendent (former)|
|First Appearance||New Normal|
|Portrayed by||Anne Heche|
Season 6 Edit
Brennan's first appearance shows her arriving to a crime scene, under the belief of Voight's lying about why he shot the man who ordered Alvin Olinsky’s death. She tells him it is being investigated as a homicide, leading for her to suspend Voight, who temporarily puts Antonio in charge of Intelligence.
Voight returns to the scene of the shooting, and realizes the presence of a surveillance camera that captured the incident. Unfortunately, Internal Affairs already got the footage an hour ago, with Brennan denying that they have it. Voight confronts Brennan, knowing she is using him for something. He still believes it’s so she can fire him, once again making reference to “white, middle-aged” cops; she once again denies this, and refuses to say anything about her motives.
Later, Antonio tells Brennan that it was Voight who made it possible to close the case. Brennan is thus motivated to apologize to Voight. She’s seen the film of the shooting now, conveniently, and is willing to persuade the powers that be that it was a good shoot, under the condition that Voight agrees to help her, help her boss get elected as Chicago Mayor. She wants him to close, or possibly not close, certain cases at her direction. Voight says his price for becoming her new “friend” is clearing Olinsky’s name so that Meredith can collect her husband’s pension.
Brennan has also made friends with Alderman Jason Collick and his wife, Allison; when the latter is murdered in True or False, she takes it personally, demanding Voight arrest someone by the end of the first day of the case. When Intelligence arrests an innocent man who kills himself in his detainment cell, Brennan becomes more afflicted, choosing to address the unit's officers were only following protocol, to which Voight agrees. During the time in which Intelligence finds out Collick is the man responsible for the murder, she is met with shock and anger; she sets up a meeting by the crime scene, and is immediate to tell her subordinates to "take him."
Her support for Brian Kelton as Mayor of Chicago comes to a head when she is threatened about previous allegations being released, and resigns from the Chicago Police Department in Confession. Since then, she acted as a confidential informant for Voight until Kelton won the election.