Prosecutors argued that the 5-4 U.S. Supreme Court ruling in 2012 should not be applied retroactively, noting that all four convicted killers had exhausted their appeals.
But the state's high court ruled Friday that the U.S. Supreme Court's ruling was so significant that it should be applied retroactively.
Assistant Attorney General Elizabeth Woodcock, who argued against holding new sentencing hearings, did not immediately return a call seeking comment on the decision and whether her office would seek review by the U.S. Supreme Court.
Friday's ruling also applies to Eduardo Lopez Jr., convicted of shooting a man during a robbery in Nashua in 1991, and Michael Soto, who supplied the gun used in a Manchester street shooting in 2007. All four were 17 at the time of the killings for which they are now serving mandatory life sentences without the possibility of parole.
In its 2012 ruling, the nation's highest court said that children are more likely to be impetuous, don't fully appreciate risks and are vulnerable to peer pressure and home environment. The ruling did not bar life sentences for juvenile killers, but said judges must weigh factors that may lead to imposition of a lesser sentence.
Chief appellate defender Christopher Johnson said Friday he does not know when resentencing hearings might be held for the four, and that scheduling will be delayed if the Attorney General's office seeks a review.
New Hampshire's justices upheld a lower court ruling last year granting the four new sentencing hearings. The state had appealed that ruling.
Tulloch is one of two Chelsea, Vermont, teens convicted of stabbing to death Dartmouth professors Half and Susanne Zantop in their home. James Parker, pleaded guilty to being an accomplice to murder and is serving 25 years to life.
The New Hampshire Civil Liberties Union was one of more than a dozen organizations to weigh in on the case. Legal director Gilles Bissonnette applauded Friday's ruling but decried the fact that all four could still wind up with life sentences.
"This is not only wrong, but the United States is the only country in the world that engages in this cruel practice of locking children up for life," Bissonnette said.
Prosecutors last year agreed to a resentencing hearing for Steven Spader, who was convicted of hacking to death a Mont Vernon woman with a machete when he was 17. Spader instructed his lawyers not to put on evidence, and he received his original sentence of life without parole plus 76 years for related crimes.