Jun. 17—A Merrimack County judge has determined a then-16-year-old was not illegally detained for hours as police investigated the killings of his sister-in-law and two young nephews in August 2022.

Public defenders for Eric Sweeney, now 17, sought to “suppress the fruits of his illegal detention” and certain statements he made to police.

Judge John Kissinger denied both requests in a 26-page order last week.

Sweeney faces three counts of first-degree murder in the deaths of Kassandra Sweeney, 25, and her two sons, Benjamin, 4, and Mason, nearly 2, in August 2022, and one count of falsifying physical evidence by discarding the murder weapon, a Taurus .40-caliber handgun. The slayings took place at their home in Northfield.

He was living in the custody of his brother, Sean Sweeney, the husband and father of the victims, at the time of the slayings.

Public defender Morgan Taggart-Hampton argued during an evidentiary hearing on April 11 that Sweeney was held beyond four hours in violation of state law, and any statement made after 3:50 p.m. on Aug. 3, 2022, should be suppressed. Prosecutors said investigators twice got permission from judges to continue to hold Sweeney.

Sweeney was arrested eight days later at Hampstead Hospital.

Kissinger ruled that Sweeney’s detention was lawful, as the investigators asked two different judges for extensions, Kissinger ruled.

Kissinger also weighed a New Hampshire Supreme Court ruling from 1985 involving a juvenile being read Miranda rights and waiving rights. Part of the consideration is the apparent mental age of the juvenile.

“The Court finds that the evidence supports a finding that Eric’s apparent mental age is consistent with his chronological age of sixteen years,” Kissinger wrote.

Kissinger also ruled that officers “plainly and clearly explained Eric’s rights.”

During the interrogation, Sweeney only asked for his brother, Sean, to be present.

Taggart-Hampton argued Sean Sweeney was emotional and slid to the floor at one point during the police interview, and might not have been available for Eric to consult.

Kissinger agreed Sean Sweeney was not capable of providing any meaningful counsel to Eric given the circumstances. However, he wrote, “the New Hampshire Supreme Court has stressed that this factor is to be analyzed solely on whether the juvenile, themselves, was afforded with the opportunity.”

Eric Sweeney voluntarily, knowingly and intelligently waived his rights, Kissinger ruled.

Eric Sweeney’s public defenders have previously said he may rely on an insanity defense.

A final pretrial hearing is scheduled for November, with the trial set to begin in December.