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Portsmouth woman pleads guilty to hindering murder probe, will testify against boyfriend

Union Leader Correspondent

July 25. 2013 8:41PM
Kathryn “Kat” McDonough, 19, of Portsmouth, breaks down during her sentencing hearing Thursday in Rockingham County Superior Court. (POOL/Rich Beauchesne/Portsmouth Herald)

Kathryn McDonough began serving a 1½- to three-year prison term Thursday as part of a negotiated plea deal that turned her into a key state witness at her boyfriend's upcoming first-degree murder trial.

McDonough, 19, of Portsmouth pleaded guilty on Thursday to charges that she lied to state and local police and delayed their investigation into the murder of Elizabeth "Lizzi" Marriott, a University of New Hampshire sophomore who disappeared last Oct. 9.

McDonough's boyfriend, Seth Mazzaglia, 30, of Dover is facing charges of first- and second-degree murder, felonious sexual assault and hindering apprehension in Strafford County for allegedly strangling Marriott at his Dover apartment.

Mazzaglia has told investigators that McDonough helped submerge Marriott's body into the Piscataqua River from the shores of Peirce Island in Portsmouth, but she was not charged with aiding Mazzaglia with the murder, or disposing of the body.

"Accessory to murder would be much more fitting as it relates Kathryn McDonough to the death of my daughter and does not suggest some victimless crime," Bob Marriott, the victim's father, said Thursday.

He was among about a dozen family members who spoke during McDonough's plea-and-sentencing hearing in Rockingham County Superior Court.

Brittany Atwood, Marriott's girlfriend, was the last person to communicate with Marriott around 8:55 p.m. on the night she disappeared. Atwood received a text message from Marriott saying she was going to her friend's "Kat's" house, investigators said.

"She was too good and pure to see the evil in Kat," Atwood said on Thursday, fighting back tears. "She was my world. My everything."

McDonough broke down and wept during Atwood's statement to the court.

Marriott's uncle, Tony Hannah of Chester, described how he and his wife came to give their niece a home while she pursued her dream of becoming a marine biologist.

Hannah said McDonough couldn't understand why McDonough took no action to prevent the murder from happening.

"Why did you let this happen? Why didn't you stop it?" he asked McDonough in court. "You could have pushed him away."

Assistant Attorney General Peter Hinckley said McDonough was in a relationship that was "manipulative and dominated by Mazzaglia," but that it was no excuse for her actions before and after the murder.

McDonough received 3½- to seven-year sentences on three charges: hindering apprehension, conspiracy to commit hindering apprehension and witness tampering. She received a reduced sentence for her expected cooperation and testimony.

No consensual sex

McDonough initially told police on Oct. 12 that she made plans for Marriott to come over to her apartment, but Marriott never showed. The two women had struck up a friendship while working at a Target department store in Greenland.

But another woman also called to the apartment the night of the murder provided a much different account.

Hinckley said that investigators later learned that McDonough had called a woman named Roberta Gerkin on Mazzaglia's cell phone on the night of Oct. 9 around 10:50 p.m. and asked her to come over to their Dover apartment.

Gerkin went to the apartment with her boyfriend, where they saw the body of a woman lying on the floor — a plastic bag covering her head and face, Hinckley said. Mazzaglia said to them, "He had gone too far and he had blacked out," according to Hinckley.

McDonough, who was in the apartment, told Gerkin and her boyfriend that the dead woman "was a student from UNH."

After Mazzaglia was arrested, McDonough met up with Gerkin in Portsmouth on Nov. 7 and asked her to tell police that she never went inside the apartment. State police were recording the conversation between the women.

Defense lawyer Andrew Cotrupi said Thursday that Marriott was going to the apartment on the night of Oct. 9 to watch a movie, rejecting claims by Mazzaglia that Marriott died during a consensual sex act.

"She is fully blameless in what happened to her," Cotrupi said, "and Kat recognizes her debt and will do what she can to see some level of justice."

Discussions with family

Hinckley said on Thursday that the terms of the sentence were appropriate given the facts of the case.

The deal was made after long discussions with the Marriott family, he said.

"No sentence is ever going to be good enough for the victim or the victim's family in this case," Hinckley said outside the courtroom after the hearing.

He said the state would be able to impose the suspended portions of McDonough's prison sentence if she did not offer truthful testimony at Mazzaglia's trial. He added that investigators have done an "incredible job" with building a case to support the first-degree murder charge.

State prosecutors said they've proposed a May trial date for Mazzaglia.

Marriott's body has not been found despite a widespread search by state, local and federal investigators. Hinckley said the search of the body is ongoing.

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