Like most prosecutors in that era, Brown adopted a tough-on-crime approach, bringing the hammer down on everything from squeegee men to drug kingpins.

On Wednesday, Brown said he would not seek re-election next fall after 27 years in office, setting the stage for the first competitive primary for Queens district attorney in decades. His decision raised the likelihood that the diverse and changing borough might elect a liberal prosecutor with a reform agenda, which would mark a sea change in local law enforcement. At least five Democratic challengers are expected to run.

The days of high crime when Brown took office are long gone. The murder rate has fallen to its lowest level since the 1950s, and prosecutors are rethinking their roles in a system where success once hinged on the number of convictions their offices amassed.

The conversation among urban liberals has turned to avoiding wrongful convictions and ending hard-nosed policies — like targeting minor offenses as a means to reducing major crimes — that critics have argued led to the incarceration of too many black and Hispanic men.

Prosecutors in Manhattan, the Bronx and Brooklyn have scaled back the prosecution of marijuana offenses and fare evasion, established conviction review units and have stopped asking for bail in minor cases. Brown, critics say, has not kept pace.

“Times have changed and it’s been really painful to observe how slow reform has taken place in Queens,” said City Councilman Donovan Richards, a Democrat who represents southeast Queens and the Rockaways. “My community and communities of color are watching this more closely and people are crying out for reform around the country.”

Brown said recently that the criticism lodged against his office are “totally unjustified.” During the two-hour-long interview, members of his executive staff highlighted a number of innovative programs the office has launched over the years. He was among the first prosecutors to create a domestic violence bureau and an office to help immigrants navigate the legal system. His office initiated dozens of programs designed as alternatives to incarceration.

Brown said Wednesday he was bowing out because his health is declining. Brown, who is 86, moves slowly, shakes with Parkinson’s disease, and relies on his police detail for help with small tasks.

Although he is still mentally alert and arrives to work at 7:30 a.m. daily, his conversation is full of long pauses. He acknowledges he lacks the vitality of his early days in office, when he made it a point to visit crime scenes. The disease, he said, has worsened in recent months, making it increasingly hard to get around.

“It was a difficult decision,” he said. “It happens to all of us. We reach the point when it is not as easy to do the work.”

Grassroots campaigns pushing for more progressive, forward-thinking prosecutors have helped transform district attorney elections in several major cities. In Philadelphia, longtime civil rights lawyer Larry Krasner, the city’s new district attorney, won over voters last year with a radically progressive campaign to end mass incarceration.

But some political strategists and law enforcement officials question whether Queens — where pockets of conservative voters remain in one of the most diverse counties in the country — will elect a prosecutor with a left-leaning platform.

Historically, the Democratic Party has had enormous influence in choosing the city’s district attorneys. The races often attract little interest, and low voter turnout allows the favorites of the political machine to win, cementing long, unchallenged tenures. Nowhere has that been more true than in Queens, where the Democratic Party has picked the county’s district attorney for decades.

But the political landscape of the borough has changed, political strategists said, pointing to this summer’s shocking defeat of longtime Democratic Rep. Joseph Crowley by newcomer Alexandria Ocasio-Cortez. Crowley’s loss, some say, signaled the end of an era, and perhaps the demise of the political apparatus that had backed Brown and has long been a force in Queens.

"He’s a product of the Queens machine and the Queens machine is on its deathbed,” said Douglas Muzzio, a professor of public affairs at Baruch College.

Still, Evan Stavisky, a partner with the Parkside Group, a political consulting firm, said the Queens Democratic Party has won more elections than it has lost and “it would be foolish to think they won’t be highly relevant to the process.”

Some candidates with progressive agendas are betting that voters are paying more attention now to racial inequities in the criminal justice system and will want to know where the candidates stand on that issue.

“Our criminal justice system is broken and the Queens district attorney’s office is ground zero,” said City Councilman Rory Lancman, who announced his run for Queens district attorney in September and whose campaign message has been likened to that of Krasner’s in Philadelphia. “The old model of a district attorney’s office — cops arrest somebody and the district attorneys put them in jail — there is a different expectation from the public as to what the district attorney’s office is supposed to be about.”

Lancman has said he would not prosecute certain low-level nonviolent offenses: possession of small amounts of marijuana; turnstile jumping; trespassing to seek shelter. He said he would not overcharge defendants, would not ask for cash bail or bond, would turn over evidence earlier to defense attorneys and would establish a wrongful conviction integrity unit.

Even former law-enforcement officials in the race have moved to the left. Gregory Lasak, a former judge who also worked as a senior prosecutor under Brown, announced he was running for the office in October. He said he too would implement similar reform policies, and would diversify the office.

“You can’t just talk about reform without having the experience,” Lasak said.

Last month, the Queens borough president, Melinda Katz, also announced she would enter the race for district attorney. Others mentioned as possible challengers include Judge George Grasso, who supervises Bronx Criminal Court, and Mina Malik, a former prosecutor in Queens and Brooklyn who is now a deputy attorney general in the District of Columbia.

Malik, whose background is Hispanic and Asian, is the only possible candidate mentioned who is not white, though others may emerge now that Brown has announced he is not running, political strategists said. Malik has not said if she will run, but she has said that the Queens district attorney’s office, which has the highest conviction rate in the city, needs a change in direction.

“The duty of a prosecutor is to seek justice, not just to convict,” Malik said. Brown, she said, “implemented reforms that were novel at the time, but we can take it further now.”