New Hampshire’s Supreme Court reversed the second-degree murder conviction of Adam Montgomery, who was found guilty in 2024 of killing his daughter in a case that received national attention.

The Court’s ruling hinged on the trial judge’s decision to allow the jury to simultaneously rule on both the murder charge and on a charge of assault that occurred months before Montgomery’s daughter, Harmony Montgomery, died.

The court found that while there was strong evidence presented at the trial that Montgomery assaulted his daughter in July 2019, the evidence that he killed her in December 2019 was comparatively weak.

“We therefore conclude that this disparity created a significant risk that the jury would rely on the strength of the evidence that the defendant struck the victim in anger in July to conclude that … he similarly — and fatally — struck the victim in December,” Justice Bryan Gould wrote in the opinion, which was released Thursday.

Montgomery’s convictions for second-degree assault, falsifying physical evidence, witness tampering and abuse of a corpse were affirmed by the court.

Separately, Montgomery is serving a sentence of 15 to 30 years for a 2023 conviction of being an armed career criminal.

The state plans to retry Montgomery on the murder charge, according to Michael Garrity, a spokesperson for the Department of Justice.

“We remain confident in the facts of this case, the evidence presented, and the exceptional work of our prosecutors, investigators, and law enforcement partners,” Garrity said in a statement. “We will continue our efforts to seek justice for Harmony Montgomery and all those who knew and loved her.”

Harmony Montgomery was five years old and living in Manchester with Adam Montgomery and his wife, Kayla Montgomery, when she died. Her death was not investigated until December 2021, when Harmony’s mother, who was living in Massachusetts at the time, reached out to state officials.

During the trial, the jury heard testimony that Adam Montgomery beat his daughter in July after she failed to supervise her five-month-old brother. Three witnesses testified that they observed Harmony with a black eye following the assault.

In contrast, the strongest evidence that Adam Montgomery killed his daughter came primarily from his wife, Kayla. She testified that, shortly after the family became homeless, Montgomery repeatedly punched her in the head.

Attorneys for Adam Montgomery argued at his trial that Kayla had killed Harmony and that he had helped her cover up the murder.

Despite exhaustive searches, Harmony’s body has never been found.