CONCORD, N.H. — The triggerman in the Pamela Smart murder trial was granted parole Thursday, nearly 25 years after he killed his school instructor’s husband and launched a global spectacle packed with lurid details of sex and manipulation.

William Flynn was 16-year-old Billy in 1990 when he and three teenage friends carried out what prosecutors said was Pamela Smart’s plot to murder Gregg Smart. Flynn pleaded guilty to second-degree murder and was sentenced to 28 years to life in prison, minus time served before trial.

A three-person state board granted Flynn parole on his first attempt Thursday, his 41st birthday. He is incarcerated in the Bolduc Correctional Facility in Warren, Maine, and participated in the hearing by telephone.

Pamela Smart, who was 22 when her husband was killed, was convicted of being an accomplice to first-degree murder and sentenced to life in prison without the chance of parole. She admitted seducing the boy but said she didn’t plan her husband’s murder.

In August, the Kennebec Journal reported that Flynn had asked the Maine Department of Corrections to be furloughed from the Bolduc Correctional Facility, where he has been held since 2013. He sought temporary release to Newcastle, where his wife since 2006, Kelly Flynn, was living. The Associated Press had previously reported that Flynn was allowed into a work release program in Warren.

The Department of Corrections in December refused to confirm whether Flynn had been granted temporary release, saying he was still considered a New Hampshire prisoner and only officials from that state could comment. But a New Hampshire official also would not comment on the temporary release request.

The March 1991 trial, complete with lurid details of a love triangle, was one of the most sensational in New Hampshire history and the first to be nationally televised live in its entirety. It provided fodder for tabloids, attracted international media attention and inspired the Joyce Maynard book “To Die For,” which the 1995 movie starring Nicole Kidman was based upon. More recently, it was the topic of an HBO documentary, “Captivated: The Trials of Pamela Smart,” which argues that Smart was unfairly convicted because of intense media coverage.

According to trial testimony, Smart was one of Flynn’s instructors in a self-awareness program at Winnicunnet High School in Hampton when she first seduced him when he was 15. She told him she needed her husband killed because she feared she would lose everything if they divorced.

Flynn testified in Smart’s 1991 trial that she threatened to break up with him if he didn’t kill her husband.

On May 1, 1990, he and 17-year-old Patrick Randall entered the Smarts’ Derry condominium and forced Gregory Smart to his knees in the foyer. As Randall held a knife to the man’s throat, Flynn fired a hollow-point bullet into his head. Randall got 28 years to life. He comes up for parole in April. Two other teenagers served prison sentences and have been released.

Smart has steadfastly denied knowing about the plot. But the state’s star witness, a teenage intern in whom Smart confided, secretly recorded her after the killing saying, “If you tell the (expletive) truth, you’ll send me to the slammer for the rest of my (expletive) life.”

“This never would have happened if it wasn’t for Pam Smart,” attorney Paul Maggiotto, who prosecuted Smart, told The Associated Press last week. “It was Smart’s manipulation of Flynn that caused this crime to occur.”

In 2008, Flynn was trying to get a reduced sentence and at his hearing apologized to Gregg Smart’s family.

“I promise you I will carry this guilt and remorse with me every day for the rest of my life,” he said.

New Hampshire court records show Flynn has won many over in Maine’s prison system. After getting an electrician’s helper license in 2002, he worked as an employee of the Maine State Prison’s electrical department, getting rave reviews from his boss. Maine state records also show Flynn passed an exam last July for a journeyman electrician’s license.

He has also worked in prisoner support groups and on a Toys for Tots program in the Rockland area. One of several correctional officers to praise him in 2008 said that Flynn had “grown from a confused teenager who made an egregious mistake into a responsible, caring individual that would be a positive addition to any community, whether inside or outside a fence.”

A spokeswoman for Smart, who was transferred in March 1993 to the Bedford Hills Correctional Facility for women in New York, told the AP that Smart took no position on Flynn’s parole bid but hopes she ultimately gets the same chance at freedom.

Flynn won’t be freed before his parole eligibility date of June 4 and only after his final parole plan is approved by the board.

Kennebec Journal staff writer Michael Shepherd contributed to this report.