New York parole board members who authorized three-time cop killer Herman Bell’s release never reviewed the minutes of the four-decades-old sentencing before making their decision — a clear violation of the law, the city’s largest police union charged Wednesday.

The Patrolmen’s Benevolent Association is trying to use this alleged misstep to demand a new hearing for Bell, who is expected to be released from prison this month, reports the New York Daily News.

Bell, 70, along with Anthony Bottom and Albert Washington, were convicted of executing Police Officers Joseph Piagentini and Waverly Jones after luring them to the Colonial Park Houses — now the Rangel Houses — on W. 159th St. with a bogus 911 call on May 21, 1971.

The three men were members of the Black Liberation Army at the time.

Jones was shot in the head and died instantly, but the three suspects took their time with Piagentini — shooting him 22 times.

Piagentini begged for his life before the end, telling Bell and his cohorts that he had a wife and two children at home.

PBA President Pat Lynch said by not reviewing the minutes from his 1979 sentencing, the board’s actions invalidated Bell’s release.

Both criminal procedure law and executive law requires that the board “obtain and consider” the recommendation of the sentencing court, Lynch said.