David Matusiewicz faces a hearing April 23 on charges he violated his probation by failing to stay away from guns and lying about his whereabouts and activities.
But a federal prosecutor and Matusiewicz's federal public defender sent a letter to the judge Monday saying Matusiewicz would not contest the charges, though he would not admit violating probation.
Instead of an evidentiary hearing with witness testimony, the government planned to offer its proof and attorneys would then argue over sentencing, they wrote.
David Matusiewicz's public defender, Dina Chavar, did not immediately return a telephone message Tuesday. A spokeswoman for the U.S. Attorney's Office had no comment.
Matusiewicz, 45, pleaded guilty to fraud and kidnapping charges in 2009 after taking his three daughters to Central America. He was arrested Feb. 11 after his ex-wife, Christine Belford, 39, and a friend, Laura Mulford, 47, were killed by his 68-year-old father, Thomas, before a scheduled child custody hearing.
Federal prosecutors initially alleged that David Matusiewicz violated his probation by not properly disclosing his whereabouts and not paying court-ordered child support and restitution.
They said Matusiewicz, in traveling to Delaware for the child custody hearing, told officials he would be staying with an uncle in Bayville, N.J., and that he failed to disclose that he spent the night before the shooting at a friend's home in Elkton, Md. Prosecutors also claimed Matusiewicz was behind on child support payments of $2,200 a month and that he has yet to pay $9,674 in restitution and a $200 court assessment from his 2009 criminal case.
Prosecutors later revised the charges, saying Matusiewicz, who was released from prison, violated prohibitions against having guns or ammunition.
Authorities executing a search warrant at his parents' Texas home the day after the courthouse shooting found a clip holding .45 caliber ammunition and two firearms in a safe inside the home. They also found three guns and more ammunition in a recreational vehicle parked just outside the home, according to court papers. More guns were found in a storage shed on the property.
Authorities also said David Matusiewicz was prohibited from associating with anybody engaged in criminal activity, but that he "knowingly associated" with his father when his father was transporting and carrying firearms in violation of gun laws in Maryland and New Jersey.
Matusiewicz's mother, who visited her son Monday, said he told her that prosecutors seem to be focused on the fact that he did not disclose where he stayed the night before the shooting.
"The only thing he said was they told him that the prosecutors are bringing up the fact that he didn't make a phone call to his probation officer in Texas," she said. "... So far as I know, that's the only thing they told him they were going to bring charges against him for."
Lenore Matusiewicz has said previously that the family left the New Jersey home and spent the night in Elkton because there was a threat of bad weather, and they wanted to be closer to the Wilmington courthouse. Because it was a Sunday, there was no way to notify David's probation officers of the change in plans, she said.
Lenore Matusiewicz said there's no reason to believe that her son knowingly violated any restrictions about being around guns, and that he was already upstairs in the courthouse when his father opened fire in the lobby.
"He was on a different floor from what happened when Tom shot Christina," she said. "He wasn't anywhere nearby."
Lenore Matusiewicz said that after his arrest, her son was put in solitary confinement and was forced to eat food with his fingers. She also said she told him that someone slid a bag of feces, with Belford's obituary attached to it, into his cell.
John Painter, a spokesman for the Department of Correction, said in an email late Tuesday, "A review has yielded no such incident being reported on an incident report, institutional grievance or informally through notification to staff or officers who routinely interact with Mr. Matusiewicz."