SUFFOLK COUNTY District Attorney Dan Conley will resign later this month to take a lobbying and litigation job with one of the city’s most high-powered firms.

Conley, who said in February that he would not seek reelection this fall, announced at a briefing Wednesday afternoon that he’ll assume the title of special counsel with the law firm Mintz Levin and a serve as a senior adviser with the firm’s lobbying arm, ML Strategies.

Conley, who has served as DA since 2002, said he has “been blessed to pursue justice” on behalf of Suffolk County residents, choking up as he thanked residents for the “trust they have placed in me.”

He said his resignation will be effective in two weeks, on September 26, at which point he expects the reins to be handed to an interim DA appointed by the governor to serve until the term expires in January. Conley said he anticipates that Gov. Charlie Baker will appoint someone currently working in the office to serve in that role. Baker’s office did not immediately return a message asking about the DA appointment.

In the five-way Democratic primary for the open seat decided last week, several candidates, including the winner, Rachael Rollins, called for a turn away from the status quo and an embrace of policies aimed at reducing incarceration and addressing racial disparities in the criminal justice system.

Conley brushed off the criticism of the office under his tenure. “Campaign rhetoric is campaign rhetoric,” he said. “I tried not to pay too much attention to it.”

Conley endorsed Greg Henning, a veteran prosecutor in his office who placed second in the primary behind Rollins.

Although Conley opposed a number of the provisions in the criminal justice reform law enacted earlier this year, including some of those related to repeal of mandatory minimum drug sentences, he has pursued several reform measures during his time in office, and pointed out that incarceration rates in the county have declined sharply in recent years.

Conley cited several of those reform initiatives, including tackling wrongful convictions with new policies on eyewitness evidence and post-conviction DNA testing that he said were “years ahead of their time.”

“As a result,” he said, “we haven’t just vacated almost a dozen wrongful convictions. For homicide, sexual assault, and other violent crimes, we’ve prevented them from occurring in the first place.”

Conley was recognized 10 years ago for his work on wrongful convictions with an award from the Boston Bar Association.

He cited a training program on ethics for prosecutors in his office, and policy of releasing the full results of investigations of every fatal police shooting, which he called “the most transparent approach anywhere in the country.”

He also highlighted a Family Justice Center he cofounded with then-Mayor Tom Menino to serve victims of domestic violence, sexual assault, and child abuse, and a juvenile diversion program that deals with youthful offenders outside the criminal justice system.

“We increasingly used a scalpel instead of a sledgehammer,” said Conley. “We took a smart on crime approach, and the results have been dramatic.”

Conley said violent crime has fallen in Boston by 35 percent, while the number of sentenced inmates in the Suffolk County House of Correction is down by 40 percent and juvenile prosecutions have been cut by almost 50 percent.

Asked if there was anything he had hoped to accomplish but wasn’t able to, Conley pointed to the difficulty of solving homicide cases, something that has been flashpoint for criticism in Boston. The issue drew national attention in July when the Washington Post reported that Boston had the widest gap in arrests for homicide of any city in the country between cases where the victim was black or white.

“I wish I could solve every single case,” said Conley. “That’s always going to be a great frustration. We gave 100 percent to this job, all of us.”

Steve Tocco, the chairman and CEO of ML Strategies, appeared with Conley for the announcement at the Suffolk DA’s office in downtown Boston. “We’re just thrilled to have him join us,” Tocco said of Conley. “He’s bright, he has a tactical mind.” Tocco said Conley’s lobbying work would focus on “city-related issues, but also security and safety issues.”

Conley, a Hyde Park native who early in his career worked as Suffolk County assistant district attorney, served as a Boston city councilor from 1994 to 2002, when he was elected DA. He made an unsuccessful bid for mayor in 2013.

Conley said he met with Rollins earlier this week. “I like her personally very much,” he said. “We had a great conversation.”

“I want Rachael Rollins to succeed if she’s elected,” he said. Rollins faces independent candidate Michael Maloney in the November general election, but is heavily favored to win.

“She has my ear and my willingness to help her,” he said, noting that they have exchanged cellphone numbers. “If she’s elected in November, I’m going to work with her 100 percent to get her off to the right start.”

Rollins, in a statement, thanked Conley for his 16 years of service as DA and his time on the City Council. “Your commitment to our city, county and the Commonwealth should be commended,” she said.

Conley, 59, said he was not tuned in to all of the lively online exchanges and debate that took place in the run-up to last week’s primary to succeed him.

“I’m not really one of those social media type people,” he said after dispelling any doubt that was the case. “I don’t instatweet or I don’t snapface.”