NEW YORK — Arminta Jeffryes was arrested while protesting police brutality. Then the police department played an unusual role in her court case.

A New York Police Department lawyer stepped in to prosecute the jaywalking charge against her, in a low-level court that usually has no prosecutors at all. While many similar cases get dismissed without any admission of guilt, Jeffryes’ lawyer says the police attorney wouldn’t agree to a dismissal unless Jeffryes said her arrest was legitimate, which she contests.

Instead, Jeffryes and another activist are trying to stop police lawyers from serving as prosecutors, a practice that’s emerged in the last two years in the nation’s biggest city.

Jeffryes and a woman charged with disorderly conduct at the same 2016 Black Lives Matter protest are scheduled for trial in criminal court this fall. A ruling also is expected soon in their civil suit challenging the police-attorney prosecutors.

To Jeffryes, a Black Lives Matter activist who’s organized protests over police shootings, it’s chilling to see police lawyers step into prosecutors’ shoes.

“Police departments are already killing us. Now they’re going to prosecute us, as well,” says Jeffryes, 23, who has repeatedly been arrested at demonstrations.

The dispute revolves around the Manhattan summons court that handles minor charges such as trespassing and open-container drinking. Tucked in a city office building, it handles tens of thousands of cases a year, almost always without prosecutors. The Manhattan district attorney’s office says it doesn’t want to expend resources on the small-time summons cases, though it did take on hundreds of Occupy Wall Street protesters’ cases in 2011 in the name of ensuring consistency.

But the NYPD lawyers have prosecuted at least 15 disorderly conduct, unpermitted vending and unspecified summons cases since December 2015, according to department data obtained by defense attorneys and the New York Civil Liberties Union.

At least five cases involved arrests at demonstrations, according to defense lawyers, transcripts and news accounts.

Police say their legal effort isn’t focused on protesters. But defense lawyers say activists are being singled out by NYPD attorneys who aren’t prosecuting cases purely on their merits.

“Their interest is not in doing justice. It’s in cutting off false-arrest lawsuits,” says Jeffryes’ attorney, Martin Stolar. “There is an inherent conflict of interest.”

Indeed, the NYPD says that it’s sick of getting sued by people who got cases dismissed, and that dismissals happen too easily when there’s no prosecutor.

It says it chooses offenders with a history of similar, unpunished misdeeds, though court transcripts show at least two people the department lawyers prosecuted in 2015 had never been arrested before. The department and DA’s office later set out written guidelines, including a defendant’s recidivism, for the police to choose cases to prosecute as the DA’s delegate.

“We do it because there have to be consequences for recidivists that intentionally engage in conduct that receives (the) summonses,” NYPD legal bureau head Lawrence Byrne said.