CHICAGO — A judge has found a Chicago police detective not guilty of involuntary manslaughter in the shooting death of an unarmed woman.

Judge Dennis J. Porter of Cook County Circuit Court, in a directed verdict, ruled that the state had failed to prove recklessness on the part of the officer, Dante Servin, 46, in the March 2012 shooting death of Rekia Boyd, 22. Judge Porter also cleared Mr. Servin of reckless discharge of a firearm and reckless conduct.

Ms. Boyd died after one of five bullets fired from Mr. Servin’s unregistered handgun pierced the left side of her head. Mr. Servin has maintained that he fired only because he felt threatened when he confronted a group at a park about the noise they were making.

The city in 2013 settled a lawsuit with the Boyd family for $4.5 million.