"I took it personally and lost control of myself," he told the jury during Krug's and Wendel's trial.

Later, while at the station house, Kwiatkowski said he noticed one of the handcuffed teens scuffling with Krug so he punched the teen several times.

From the day he took his plea deal, the former Buffalo cop became a much anticipated witness in the case against Krug and Wendel.

During his time on the stand, he faced questions about his disciplinary record and mental health. He suffers from post-traumatic stress disorder and, on Wednesday, told Skretny he retired from the police department because of his condition.

"I'm not the same person I was 10 years ago," Kwiatkowski said.

His record includes a 2006 on-duty confrontation with a fellow officer, Cariol J. Horne, during a violent arrest. She claimed Kwiatkowski was choking a man he and other officers were placing under arrest, while he alleged Horne jumped on his back while he was trying to subdue the man. She was fired from her job following an internal affairs review and a disciplinary proceeding.

Like the prosecution, Kwiatkowski's defense lawyer asked Skretny to consider the significance of his client's testimony against his fellow officers.