The New Hampshire father convicted of murdering and hiding the body of his daughter Harmony Montgomery had his conviction tossed by the state’s highest court on a legal technicality.

Adam Montgomery’s 2024 second-degree murder conviction was reversed by the state’s Supreme Court Thursday after his attorneys successfully argued the charge should have been tried separately from an assault charge against his daughter that was also heard at his trial.

The supreme court ruled unanimously to overturn the murder charge, arguing the evidence of assault was stronger than murder – and that trying them together would have biased the jury towards finding Montgomery guilty of murder.

“There was a significant risk that the jury would draw the impermissible inference that because the defendant assaulted the victim before by striking her in the head, he must be the one who fatally assaulted her in December by again striking her in the head,” the ruling read.

State prosecutors said they would pursue a new murder trial.

Montgomery was accused of battering 5-year-old Harmony after she soiled the car he was living in with his wife and three kids in Dec. 2019, allegedly beating her in the face so badly that she died.

It allegedly took the family hours to realize the girl was dead, and Montgomery allegedly spent the next three months moving the body – stuffed in a duffel bag — from hiding place to hiding place, his wife testified at the murder trial.

Those hiding places included the trunk of a friend’s car, a cooler at an apartment building, a workplace freezer, and a ceiling vent at a homeless shelter – only moving it from those vents after people started complaining about a smell.

Harmony’s remains were never found, but prosecutors alleged he likely disposed of it somewhere around Boston in 2020.

The girl wasn’t even reported missing until 2021 – two years after her death.

Much of the trial was based on testimony from Montgomery’s wife, Kayla, who struck a deal with prosecutors to receive 18 months in prison for lying about when she last saw her step-daughter.

Montgomery was serving a combined 56-years-to-life for the grisly crime, 45 years of which were for the murder conviction.

His other charges – on top of assault — included abuse of a corpse, witness tampering, and falsifying evidence.

Montgomery will not be sprung from jail because of the overturn, however, as he is also serving more than 32 years for a separate gun conviction.

Prosecutors expressed confidence that Montgomery would be convicted of murder again once he goes back to trial.

“We remain confident in the facts of this case, the evidence presented, and the exceptional work of our prosecutors, investigators, and law enforcement partners,” said a representative for the state attorney general office.

“We will continue our efforts to seek justice for Harmony Montgomery and all those who knew and loved her.”