A Chicago Police sergeant fired this month over the 2009 death of woman he says shot herself with his gun while the two drank together inside her apartment sued the city Monday to try to get his job back.

Steven E. Lesner, 48, called the Chicago Police Board’s July 17 decision to fire him “clearly erroneous” in his three-page complaint filed in Cook County Circuit Court. The 20-year police veteran also pointed out that police Supt. Garry McCarthy had recommended he be suspended for 60 days over the death of Catherine Weiland, 47.

In explaining its decision to overrule McCarthy, the police board wrote, “With all due respect to the Superintendent, where the pattern of misconduct is as extensive as we find in this case and the consequences of the misconduct are so grave, the board finds that discharge is the only appropriate penalty.”

Neither Lesner nor his attorney, Thomas J. Pleines, could be reached for comment.  A city Law Department spokesman declined to comment, citing the pending lawsuit.

Lesner was an Albany Park District sergeant when he responded to Weiland’s call for help during an argument with her boyfriend at a restaurant in February 2009. Lesner drove Weiland home — buying her a bottle of wine along the way — and returned to her Northwest Side apartment with more liquor after his shift ended.

There, “Lesner and Weiland watched television, drank and socialized for a period of approximately 30 minutes,” according to Lesner’s lawsuit, which also says he’d removed his gun and holster “and placed them alongside where he was sitting.”

Lesner “then got up and went to the bathroom. While he was in the bathroom he heard a gunshot and returned to the living room to find that Weiland had committed suicide with Lesner’s weapon.”

Weiland, according to police reports, was found seated with the gun in her lap. Authorities found that the bullet entered her right temple, but the only gunshot residue found was on her left hand. Evidence technicians found no gunshot residue on Lesner’s hands, but police noted Lesner had washed his hands by the time they tested them.

Weiland lived in a three-flat with her father and brother, both of whom have since died. They told police in 2009 she’d had mental health issues.