Daniel F. Conley, the Suffolk district attorney who has overseen some of the state’s most high-profile cases, including the double-murder trial of former New England Patriots player Aaron Hernandez and the death of 2-year-old Bella Bond, said Tuesday that he will not seek reelection in November.
Conley, a former Boston city councilor and unsuccessful mayoral candidate in 2013, has served for 16 years as the top state prosecutor for Boston, Chelsea, Revere, and Winthrop.
“This decision has not been an easy one, but it is the right one,” the Hyde Park native said in a statement Tuesday. “I have long believed that we who are privileged to lead and serve as elected officials must also be willing to give others an opportunity to do the same.”
Conley, 59, a Democrat, was appointed in February 2002 by then-acting governor Jane M. Swift to fill the unexpired term of Ralph Martin, who resigned to join the private sector.
He was elected to a full four-year term later that year and reelected without opposition for three more terms.
Conley, responding to a question about his next career steps, said in an e-mail that he is looking “at a number of options right now, primarily within the practice of law.”
Conley’s announcement quickly prompted speculation about who may run to succeed him in one of the state’s highest-profile law enforcement jobs. Among the potential candidates: Boston City Councilor Michael Flaherty and lawyer Shannon McAuliffe.
Prior to becoming district attorney, Conley was one of a handful of state prosecutors named to the first Massachusetts anti-gang-violence task force during the late 1980s and early 1990s, according to his online biography.
As the district attorney, he worked to extend the statute of limitations on sex crimes against children, created a witness protection fund to support victims and witnesses of violent crime, and drafted a safe harbor provision to the state’s landmark human trafficking law to treat prostituted youth as victims rather than offenders, according to his office.
“It’s always been an aspirational goal to solve every homicide and deliver some measure of justice to every victim and family,” Conley said in the e-mail. “That may not be possible, but setting the goal means trying to reach it, to the best of my ability, for every family, every time.”
Boston Police Commissioner William B. Evans said Conley was fair and impartial, and had a high standard when it came to bringing charges.
Conley was “very concerned about the rights of the defendants” but also never forgot the victims of violent crimes, Evans said in a telephone interview.
“No one cared more about the victims and bringing justice to those families than he did,” said Evans.
In a statement, Boston Mayor Martin J. Walsh called Conley a “committed, hard-working district attorney. . . . I wish him all the best going forward and thank Dan for his many years of service.”
But one prominent criminal defense lawyer criticized Conley for what he considered to be his failures.
“My biggest disappointment with him is that he failed to recognize that we incarcerate too many people,” said John “Jack” Cunha, who represented Edward Washington, who was acquitted in a 2010 quadruple slaying in Mattapan that was considered to be one of the worst homicide cases in recent Boston history.
“And he failed to recognize that things like mandatory minimums have not worked. He failed to recognize that taking discretion away from judges and giving it to prosecutors is not a way to run a fair criminal justice system.”
In response to that criticism, Conley said in an e-mail that Massachusetts has the second-lowest rate of incarceration in the country, and has reduced juvenile commitments to the third-lowest rate in the country.
Darnell L. Williams, president and CEO of the Urban League of Eastern Massachusetts, said Conley has become a strong ally for Boston’s black community.
While there was “creative tension” in the past between himself and Conley as to whether Conley’s office could impartially evaluate questionable behavior by police, Conley also pushed for transparency of probes into police departments, he said.
“He has evolved his position there, and he has to be applauded for that,” said Williams.
Conley has had a willingness “to be open with police-involved shootings,” said Tanisha Sullivan, the president of the NAACP Boston branch.
Rashaan Hall, the director of the racial justice program for the ACLU of Massachusetts, acknowledged his group has clashed with Conley over some issues, including mandatory minimum sentencing and a state wiretapping statute.
Still, Hall, who worked as prosecutor under Conley for eight years, said the DA has worked “hard to serve the people of Suffolk County.”
“As a former employee, I can tell you he did right by me,” said Hall. “He created meaningful opportunities for me to engage with the communities I was working with.”
J.W. Carney Jr., a criminal defense attorney based in Boston, said Conley’s office cultivated a “group of prosecutors who had exceptional skill and unwavering commitment to justice.” Carney said Conley “did an outstanding job prosecuting the most difficult cases in Massachusetts.”
“He has shown great personal integrity and fairness,” said Carney.
Norfolk District Attorney Michael Morrissey, who is the president of the Massachusetts District Attorney Association, said Conley handled the glare of high-profile murder cases with aplomb.
“He is usually on the hot seat,” said Morrissey, who worked with Conley in private practice for at least six years. “At one time half of the murders in the state were in Suffolk County. He was dealing with issues of witness intimidation, murders. It’s probably one of the tougher jobs out there.”
Citing the case where Hernandez was cleared of committing a double murder in 2012, Morrissey said Conley was tenacious in pursuing justice.
“I can’t tell you that that result was what he was looking for, but I can tell you that he never backed down from trying a difficult case,” he said.
In 2015, Conley prosecuted the case of Bond, the toddler first known as “Baby Doe” after her unidentified remains washed ashore in a trash bag in Boston Harbor.
Conley’s office successfully prosecuted the ex-boyfriend of the girl’s mother for second-degree murder.
Martin W. Healy, chief legal counsel for the Massachusetts Bar Association, said Conley was progressive in his willingness to identify and correct potential wrongful convictions.
“I think in terms of his legacy he’ll be known as a solid prosecutor but also as someone who kept pace with modern times,” said Healy.
Speculation was rampant Tuesday regarding who would run to succeed Conley.
Flaherty acknowledged he was interested in possibly running for DA, while praising Conley as a tireless, “professional prosecutor.”
“I have always been interested in being the Suffolk County district attorney,” he said in a statement.
McAuliffe, a lawyer and the former director of an antiviolence youth program in Greater Boston, plans to run for Suffolk DA, according to a political consultant helping to kickstart her nascent campaign.
McAuliffe already had her eye on the office before Tuesday’s surprise announcement that Conley would not seek reelection, the consultant said. She is expected to make a formal announcement in the near future.
Akilah Johnson of the Globe Staff contributed to this report. Travis Andersen can be reached at firstname.lastname@example.org. Follow him on Twitter @TAGlobe. Danny McDonald can be reached at Daniel.McDonald@globe.com. Follow him on Twitter @danny_mcdonald.