Brooklyn prosecutors moved Wednesday to vacate nearly 400 criminal convictions based on the work of 13 former New York Police Department officers later found guilty of crimes themselves. Only 12 percent of the 378 convictions being eyed by the office of Brooklyn District Attorney Eric Gonzalez are felonies; most of them are low-level drug or traffic offenses, some of them dating back more than 20 years.

It marks the sixth largest mass dismissal of convictions in U.S. history, according to federal data, Gonzalez said.

The district attorney added that his team had not necessarily found misconduct in each case, but that they “no longer have confidence” in their validity, given that the officers who worked on them were eventually convicted of a gamut of charges, including perjury, corruption, and civil liberties violations. One ex-officer, Richard Danese, was convicted of disorderly conduct in 2009 after a bizarre case in which he arrested a teenage boy and dumped him in a Staten Island swamp, according to The New York Times. Read more at The New York Times.