Teen charged in Northfield triple murder 'may rely' on insanity defense
Mar. 6—A Northfield teenager charged with first-degree murder in the shooting deaths of his sister-in-law and two young nephews has notified the court he may pursue an insanity defense.
Eric Sweeney, 17, is facing three counts of first-degree murder for allegedly killing 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.
He had been living on Wethersfield Drive in Northfield with his brother, Sean, and his family.
Public defender Lauren Prusiner filed the notice of insanity defense last week "with authorization from Eric." He reserves the right to withdraw it later or to advise lawyers not to pursue an insanity defense at trial, according to the notice.
A two-week trial is set to begin on Dec. 2 after jury selection, which could take several days.
The Attorney General's Office is "experienced in responding to such defenses," according to a statement, but said it can't comment on how this case is similar or different from other insanity defenses.
Unlike determining competency, an insanity defense tries to show the person was mentally disturbed at the time of the crime, and the defendant is able to assist their lawyers, said Nashua defense lawyer Chuck Keefe, who has no connection to the case.
Such a defense requires both the defense and prosecution to call experts.
Sweeney's lawyers say the teenager's detention on the day of the killings was illegal, and they want to suppress evidence from a body search. Investigators must contact the courts if a minor is held for more than four hours to determine placement, according to the defense.
Extension secured
Police and the Attorney General's Office secured an extension of custody from a Laconia Family Court Judge.
The defense says Sweeney stayed more than nine hours at the police station, where items were collected and sent to the state police lab.
"The search warrant for Eric's body and all evidence collected from the execution of said warrant must be suppressed as it was gathered beyond the four hours law enforcement was legally allowed to keep Eric in custody pursuant to the statute," the filing states.
The defense also is seeking to block statements made by Sweeney to state police troopers. The interrogation took place a week after his 16th birthday. He is being tried as an adult.
Sean Sweeney, who is Eric Sweeney's guardian, called 911 saying his brother reported the murder. Eric Sweeney claimed "someone had broken into the home and 'killed them all,'" according to court documents.
Officers "began to use language that Eric 'owed' Sean Sweeney for acting as his guardian and stated that Mr. Sweeney must now bury his young sons," the documents read.
Sean Sweeney was in the interrogation room but did not advise Eric.
"Mr. Sweeney stood in the corner of the room. During the interrogation itself, he put his hands on his head and over his face," the document says. "He slid down the wall he was standing against and sat on the floor with his head in his hands. Understandably, he was in no position to assist or advise Eric about his waiver."
Police logs show Sean Sweeney had called Northfield police with concerns twice in the two months leading up to the murders of his wife and sons. Twelve days before the murders, Sean Sweeney told police he had found a weapon in his garage and others in the woods and said he feared for his children's safety, according to police records.
Eric Sweeney's defense team includes Shea Sennett and Morgan Taggart-Hampton.
A final pretrial hearing is scheduled for Nov. 4.
