CONCORD, N.H. (AP) — A man who pleaded guilty as a teenager to the 2001 stabbing deaths of two married Dartmouth College professors is challenging his life-without-parole sentence, saying that the New Hampshire Constitution prohibits it.

Robert Tulloch was 17 when he killed Half Zantop and Susanne Zantop in Hanover as part of a conspiracy he and his best friend concocted to rob and kill people before fleeing to Australia with their ill-gotten gains.

A hearing was scheduled Wednesday in Grafton County Superior Court to consider legal issues raised in Tulloch’s case.

Tulloch, 41, awaits resentencing at a later date, following a 2012 U.S. Supreme Court decision that said mandatory life sentences without parole for juveniles amounts to “cruel and unusual” punishment. Another opinion made that decision retroactive, giving hundreds of juvenile lifers a shot at freedom. In 2021, the court found that a minor did not have to be found incapable of being rehabilitated before being sentenced to life without parole.

At least 28 states have banned such sentences for crimes committed when the defendant is a child. But efforts to pass similar legislation in New Hampshire have not succeeded.

The New Hampshire Constitution says no court of law “shall deem excessive bail or sureties, impose excessive fines, or inflict cruel or unusual punishments.”

That language would include sentencing someone to life without parole when they commit a crime as a child, Tulloch’s lawyer, Richard Guerriero, wrote in a memorandum. He also argued that the state constitution’s language is broader and offers more protection than the U.S. Constitution’s.

The American Civil Liberties Union of New Hampshire and other organizations filed a brief in support of Tulloch.

Prosecutors said in court documents that Guerriero’s argument is not compelling. They have said it is possible they will ask for a similar life-without-parole sentence for Tulloch.

If a judge finds that the state constitution permits life-without-parole sentences for crimes committed by children, Guerriero also asked for findings that a defendant is incapable of change and proof beyond a reasonable doubt that such a sentence is appropriate.

Tulloch is the last of five men who awaits resentencing under a state supreme court ruling. Three were resentenced to lengthy terms with a chance at parole. One was resentenced to life without parole after refusing to attend his hearing or authorize his attorneys to argue for a lesser sentence.

Tulloch’s friend, James Parker, 40, was released from prison on parole in June. He was 16 when the crimes were committed. Parker had pleaded guilty to being an accomplice to second-degree murder in the death of Susanne Zantop. He served nearly the minimum term of his 25-years-to-life sentence.

Parker agreed to testify against Tulloch, who had planned to use an insanity defense at his trial. But Tulloch changed his mind and pleaded guilty to first-degree murder.

The teens, bored with their lives in nearby Chelsea, Vermont, wanted to move to Australia and estimated they needed $10,000 for the trip. They eventually decided they would knock on homeowners’ doors under the pretext of conducting a survey on environmental issues, then tie up their victims and steal their credit cards and ATM information. They planned to make their captives provide their PINs before killing them.

For about six months, they had tried to talk their way into four other homes in Vermont and New Hampshire, but were turned away or found no one home.

Parker, who cooperated with prosecutors, said they picked the Zantop house because it looked expensive and it was surrounded by trees. Susanne Zantop, 55, was head of Dartmouth’s German studies department and her husband, Half Zantop, 62, taught Earth sciences.

Parker and Tulloch were arrested weeks later.