CONCORD — A legal challenge over whether the sentence imposed on the convicted murderer of two Dartmouth College professors violates the state’s constitution has been sent back to a lower court by the New Hampshire Supreme Court.

The state’s highest court declined to take up the question of whether Robert Tulloch’s two life sentences without possibility of parole are constitutional, ordering that the issue first be dealt with at a resentencing hearing that Tulloch has been seeking for years in Grafton County Superior Court.

“Prior to resentencing, the trial court shall rule upon (Tulloch’s) 2018 motion to declare life sentences without the possibility of parole unconstitutional for juvenile offenders,” according to a one-page order dated April 11.

Tulloch, 41, is serving the two life sentences after he pleaded guilty to murdering Dartmouth professors Half and Susanne Zantop at their home in Hanover when he was 17 years old. His accomplice, James Parker, 40, was 16 at the time.

The two high school friends from Chelsea tricked their way into the Zantops’ home and stabbed them in a robbery attempt.

Parker was paroled last year after spending more than half his life behind bars.

For years, Tulloch has been seeking to be resentenced on the grounds that his sentence without the possibility of parole is invalid following the U.S. Supreme Court ruling in 2012 that such mandatory sentences for juvenile murderers are unconstitutional.

Tulloch’s challenge was being argued in Grafton County Superior Court — where his trial would have been held had he not pleaded guilty to two counts of first-degree murder in 2002.

But in February, Judge Lawrence MacLeod referred the question of whether Tulloch’s lifetime sentence is unconstitutional to the state Supreme Court. The judge contended that there has not been enough precedent established in New Hampshire to provide judicial guidance.

State prosecutors — the Attorney General’s Office has led the prosecution, not the Grafton County state’s attorney — had wanted the constitutionality question hashed out first in the trial court before being appealed to the state Supreme Court.

The Supreme Court’s remand order essentially sends the matter back to the trial court where prosecutors wanted it heard all along.

An attorney for Tulloch did not respond to an email for comment.

But MacLeod in his statement to the Supreme Court — which was largely adopted from Tulloch’s petition because the state did not file a proposed appeal brief — said the issue was too momentous to be taken up at the trial court level.

“Given the stakes of the legal questions presented — for the court, for the judiciary’s reputation, and for every person who is serving or may serve a life without parole sentence for an offense committed as a minor — the court must make the most informed possible decision at resentencing,” MacLeod wrote, adding that “no clear majority exists on any of the questions presented … the (trial) court cannot rely on the weight of authority from sister jurisdictions to ground a ruling.”

A key issue in Tulloch’s case is the question of “permanent incorrigibility,” which the 2012 U.S. Supreme Court decision cited as an exception to the unconstitutionality of a lifetime sentence without possibility of parole. The justices ruled it could be applied to the “rarest of offenders” who demonstrate no ability for rehabilitation or are hopelessly depraved.

At a hearing in Grafton court last September, Tulloch’s attorneys and state prosecutors disagreed over the burdens of proof for both the finding of permanent incorrigibility and the facts the sentence is based on, according to the interlocutory statement.

In the Supreme Court’s brief two-sentence order, the three justices gave no reason for remanding the constitutionality question to the trial court. (Chief Justice Gordon MacDonald, the son of a Dartmouth professor who grew up in Hanover and himself graduated from Dartmouth, did not participate and Justice Anna Barbara Hantz Marconi is on administrative leave.)

No further court hearings have been set in the case as of Wednesday afternoon.

Contact John Lippman at jlippman@vnews.com.