CONCORD, N.H. — A Vermont man who was 17 when he and a friend killed a pair of married Dartmouth College professors 25 years ago is seeking to have his life sentence reduced to a minimum of 30 to 40 years.

Robert Tulloch, now 43, was automatically sentenced to life in prison without parole after pleading guilty to first-degree murder in the stabbing deaths of Half and Susanne Zantop in 2001. But the U.S. Supreme Court ruled in 2012 that mandatory life-without-parole sentences are unconstitutional for juveniles, and then applied that decision retroactively.

The rulings gave hundreds of young men sentenced to life in prison a chance at freedom, including five men serving life sentences in New Hampshire for murders they committed as teenagers. Tulloch’s resentencing hearing, the last of five, begins Monday in Grafton County Superior Court.

The state has not said what sentence it will seek. But in a court filing last week, Tulloch’s attorneys argue that a minimum sentence in the range of 30 to 40 years is appropriate, based on a review of other juvenile murders in New Hampshire and cases across the country that were affected by the Supreme Court rulings.

Attorneys Richard Guerriero and Oliver Bloom also said Tulloch’s prison records show he has matured and, after some initial misconduct early on, has had no major infractions since 2012 and no minor infractions since 2017. “The vast majority of his articles are for possession of too many books,” they wrote.

Citing Tulloch’s therapy records, they said he has expressed “significant remorse” for what he considers a heinous and unforgivable crime, his “twisted youthful thinking” and his “good capacity for empathy.”

According to Tulloch’s friend James Parker, the teenagers were bored with their lives in Chelsea, Vermont, when they hatched a plan to kill strangers, steal their money, and move to Australia. For several months, they knocked on doors in New Hampshire and Vermont pretending to be conducting an environmental survey before the Zantops let them in. Susanne Zantop, 55, was head of Dartmouth’s German studies department and her husband, Half Zantop, 62, taught Earth sciences.

Parker, who was 16 at the time, told prosecutors that Tulloch stabbed Half Zantop and then ordered Parker to attack Susanne Zantop. Tulloch also stabbed her. Fingerprints on a knife sheath and a bloody boot print linked the teens to the crime, but after being questioned by police, they fled Vermont and hitchhiked west. They were arrested at an Indiana truck stop weeks later.

Parker, who cooperated with prosecutors and pleaded guilty to being an accessory to second-degree murder, was paroled from prison in 2024 at age 40, having served almost the minimum of his 25 years to life sentence.

“I think it’s unimaginably horrible,” Parker said during his parole hearing when a board member asked him what he thought of what he did. “I know there’s no amount of time or things I can do to change it or ease the pain I’ve caused.”

The Supreme Court rulings addressed only mandatory life sentences without parole for juveniles, leaving the United States the only country that allows discretionary life sentences for juveniles. Twenty-eight states and the District of Columbia have banned the practice, while five other states allow it but no one serves that sentence, according to the Campaign for Fair Sentencing of Youth.

New Hampshire lawmakers have rejected attempts to end life sentences for juveniles, but Tulloch’s case could bolster future efforts. After Tulloch argued in 2018 that sentencing juveniles to life in prison without parole violated the state constitution, the judge asked the state Supreme Court to weigh in, but it refused. Last July, Superior Court Judge Lawrence MacLeod agreed with Tulloch and concluded that the Constitution categorically prohibits these types of sentences as “cruel or unusual” punishments.

Among juvenile lifers nationwide who have been resentenced after the U.S. Supreme Court rulings, more than 75% have received sentences of less than 40 years, according to a study published in 2024 in the Journal of Criminal Justice.

In New Hampshire, a man was resentenced to life in prison without parole after refusing to attend his hearing or authorize his attorneys to argue for a lesser sentence. Others received sentences of 25, 40 and 45 years to life in prison.