A former Suffolk County prosecutor will take over as the county's district attorney for the next year, preparing to serve in what his former boss expects will be a "more traditional prosecutor's role" as reform-minded DA Rachael Rollins ascends to a federal post.

Gov. Charlie Baker on Thursday named Kevin Hayden, who since 2015 has served as chair of the state's Sex Offender Registry Board, to serve the remainder of Rollins's term when she departs to become U.S. attorney for Massachusetts.

Hayden will take over as the county's interim top prosecutor on Monday, when Rollins plans to take the oath of office for her new role. His term will last until the next Suffolk DA -- whom voters will select in the Nov. 8 election -- is sworn in.

The appointment marks a return to the office for Hayden, who spent about a decade as a prosecutor in Suffolk County after he graduated from Boston University's School of Law, and it could offer him a foundation for a campaign should he choose to run for a full term.

Former Suffolk County District Attorney Daniel Conley, who oversaw Hayden for six years during his tenure, said he believes the SORB chair will make an "excellent leader" as the new top prosecutor.

"Like all good prosecutors, and I like to think I was the same way and I imparted this on the staff who worked for me, we recognize human frailty and we recognize that people who make mistakes are one class of individuals that come before the court. But there's also another class of defendants who are very serious and violent," Conley said in an interview with the News Service. "When Kevin was an assistant DA, he focused on both. He understood and he could distinguish the difference."

Hayden, a Democrat, served in the Suffolk County DA's office from January 1997 to April 2008.

Conley, who today works as an attorney at Mintz Levin in Boston, recalled that at the start of his tenure as DA in 2002, Hayden was a district court prosecutor and later rose through the ranks into leadership positions.

During his time in the DA's office, Hayden served as chief of the Safe Neighborhood Initiative Unit and as assistant district attorney for the Anti-Gang Unit, the Homicide Response Team, the Juvenile Unit and for the Boston Municipal Court, according to Baker's office.

Hayden departed in 2008 to join a private law practice, Conley said, and later began serving in general counsel and active executive director roles for the Sex Offender Registry Board.

In 2015, Hayden became the agency's chair, replacing Gov. Deval Patrick appointee Anne Conners.

"I started 25 years ago as a young prosecutor right here in Suffolk County. Over the years it has remained the desire of my heart to serve and protect our many diverse communities. So it's truly my distinct honor and privilege to be called home by the Governor through this appointment," Hayden said in a statement. "With unwavering and compassionate commitment I know it will be Suffolk County's continued legacy to shine as a beacon in the fields of public safety and criminal justice."

Announcing his pick, Baker praised Hayden as "a dedicated public servant with a proven record of commitment to equitable justice and community engagement."

"A veteran of the District Attorney's Office, where he led the Safe Neighborhood Initiative Unit and devoted himself to leading community-based violence prevention outreach and programming, Chairman Hayden is equipped with the experience and knowledge necessary to serve in this role," the Republican governor said. "I thank District Attorney Rollins for her service and commitment to the people of Suffolk County and look forward to continuing to work with her in her new role as US Attorney."

Rollins, a Democrat, will leave before the end of her first term to become the top federal prosecutor in Massachusetts.

In a Thursday afternoon statement, Rollins offered Hayden "heartfelt congratulations."

"District Attorney Hayden's professional experience speaks to his prioritization of serious and violent offenses and addressing the needs of our communities," Rollins said. "I look forward to working hand-in-hand with him as he ascends to his new role and I ascend to mine."

Her office did not respond to a question about whether Rollins formally submitted a recommendation to Baker naming her preference for a successor.

Earlier this year, Rollins tweeted, "FYI, when DA's leave, at least all the men that did before I was elected, they recommend (tell) the Governor who should replace them."

Rollins on Thursday thanked Baker "for our numerous conversations and his thoughtful consideration of the candidates who sought his appointment to serve out the remainder of my term."

"The District Attorney holds great power in the lives of those who come into contact with the criminal legal system -- whether as a victim, survivor, witness, charged individual or an impacted family or community member," Rollins said. "In selecting his appointment for Suffolk County's top law enforcement official, Governor Baker took great care to choose an individual with subject matter expertise, leadership experience and a respect for and fluency in the different concerns and needs of each of the neighborhoods that make up Suffolk County."

Her approach as district attorney, which she outlined in a "progressive prosecution" strategy in March 2019, called for looking to divert or dismiss many nonviolent, low-level offenses. It also at times drew criticism from the Baker administration.

Conley said he anticipates Hayden will "cut his own path."

"I expect Kevin to pursue a more traditional prosecutor's role, one that is victim-centered and focused on serving victims and keeping neighborhoods as safe as they possibly can be," Conley said. "That's the kind of leader I expect that he will be because that's the kind of prosecutor he was as a young lawyer."

Voters will choose the next Suffolk County district attorney this fall. Hayden did not say on Thursday if he planned to launch a bid for a full term, but Conley said he hopes his acquaintance of two decades decides to do so.

"This is a great opportunity for the voters of Suffolk County to look at Kevin Hayden's performance over the next eight months, for sure, until the Democratic primary and then 11 or so months until the final election," Conley said. "My expectation is if Kevin does the job the way I expect he will based on my 20 years of knowing him, I think he should easily win election."

Conley could serve as precedent, too: a Democrat, he was first appointed by Republican Acting Gov. Jane Swift to serve out the remainder of former DA Ralph Martin's term before winning election later that year.

Biden in July nominated Rollins to serve as the next top federal prosecutor for the Bay State, and the Senate confirmed her in December via a party-line vote with Vice President Kamala Harris breaking a 50-50 tie.

Hayden's appointment will also create a vacancy as chair of the Sex Offender Registry Board. Baker's office said the administration is reviewing candidates to fill that role.