A New York court set aside 46 convictions in cases that featured testimony from a former Police Department detective who had perjured himself, the Queens district attorney announced on Thursday.

The district attorney, Melinda Katz, asked the Queens Criminal Court to throw out the convictions after the detective, James Donovan, pleaded guilty to perjury in May 2023, Ms. Katz said in a statement.

Mr. Donovan’s plea led to a review of his previous cases by the district attorney’s Conviction Integrity Unit, which identified 46 convictions where Mr. Donovan was the primary witness. The cases were all misdemeanors, according to the district attorney’s office, with charges ranging from disorderly conduct and trespassing to three-card monte.

“We cannot stand behind a conviction where the essential witness was a law enforcement officer convicted of a crime that irreparably impaired his credibility,” Ms. Katz said in the statement. “I believe it is necessary to take this step to protect the public’s confidence in the justice system.”

Since the district attorney’s office created the Conviction Integrity Unit in 2020, 148 convictions have been set aside, including the 46 announced on Thursday, Ms. Katz said.

On Aug. 11, 2021, Mr. Donovan testified before a Queens grand jury about an arrest he said he made the previous November, when he said he found a suspect sleeping in the back seat of a car. Mr. Donovan said that he opened the car door, pulled the man out and handcuffed him. Where the man’s head had been lying in the back seat, Mr. Donovan said, he saw a white and pink gun.