The Internal Affairs division of the Los Angeles Police Department investigates incidents and plausible suspicions of lawbreaking and professional misconduct attributed to officers on the force.
When Danny Sofer shot an armed civilian called Zayed Al-Thani, Internal Affairs was brought in to investigate the case. Later, someone called Internal Affairs and told them that Danny was dealing marihuana from her car. Detectives Branning and Simpkins went to the Barn to investigate and found four ounces of marihuana under the seat of her car. She alleged that someone put it there and Internal Affairs believed her.
Also, when Vic and Corrine Mackey had an argument due to a misunderstanding, she filed a domestic dispute complaint. As a result, a detective from Internal Affairs went to the Barn and arrested Mackey.
After Monica Rawling began working as captain of the Barn, she authorized an Internal Affairs investigation into Vic Mackey and the Strike Team, due to their bad reputation. The day she was fired, the agent assigned to investigate them informed her that they had evidence that Curtis Lemansky had stolen a brick of tar heroin from the house of a drug dealer and failed to register it as evidence.
The investigation on the Strike Team continues, this time led by Lieutenant Jon Kavanaugh. Eventually, he filed charges against the whole Strike Team for several charges. Charges were dropped when Curtis Lemansky was murdered.
Jon Kavanaugh's investigation was reopened when he told Assistant Chief Roy Phillips that he thought Mackey was responsible for Lem's death. However, Kavanaugh was arrested when he confessed to doctoring evidence and seeking a false statement from witness Emolia Melendez.