Prosecutor: Mazzaglia Killed UNH Student After She Rejected Him

DOVER, N.H. (AP) — The man charged with killing a Massachusetts coed became enraged when she denied his sexual advances, snuck up behind her and choked her with a rope before raping her, prosecutors said at the opening of his trial on Wednesday

Seth Mazzaglia, 31, is charged with first-degree murder in the death of Elizabeth "Lizzi" Marriott. He has said she died during rough consensual sex and his lawyers argued that his then-girlfriend was responsible for Marriott's death.

Marriott, of Westborough, Massachusetts, was a 19-year-old student at the University of New Hampshire who was lured to Mazzaglia's apartment by his girlfriend, Kathryn "Kat" McDonough, on Oct. 9, 2012.

During opening statements, the prosecution painted a lurid picture of Mazzaglia as sexually dominant and said he took Marriott by force when she wouldn't come to him willingly.

Assistant Attorney General Peter Hinckley said that Mazzaglia asked Marriott for sex after playing a game of strip poker at the apartment he shared with McDonough.

"Lizzi said 'no,'" Hinckley said.

Mazzaglia then said he was going to have sex with McDonough while Marriott watched, Hinckley said.

"She rejected the master again, in his home, where he got whatever he wanted sexually," Hinckley said. "So he took what Lizzi denied him."

Hinckley said Mazzaglia put on gloves, walked to the back of the couch where the two young women were watching a movie and slipped a rope around Marriott's neck.

"He yanked back hard and Lizzi never had a chance," Hinckley said. "The defendant struck quick, without warning and with absolutely no mercy. Lizzi had time to let out a quick, terrifying cry but had time for little else. He choked her for minutes until she could no longer deny him."

Then, Hinckley said, Mazzaglia raped her as McDonough watched.

Marriott's body was thrown into the Piscataqua River and has not been recovered.

Marriott's parents sat in the front row of the courtroom, her mother softly weeping at times.

Defense lawyers put the blame on McDonough, saying Marriott died when McDonough trussed her with a harness and collar and suffocated her during a rough sex act.

The defense team cast her as the sexual manipulator in her relationship with Mazzaglia and said she lied and will testify against him to get a more lenient sentence.

Defense lawyer Joachim Barth said Mazzaglia was overwhelmed by panic after Marriott died and his judgment and conduct after was "compounded by his love, his obsessive love, for Kat."

McDonough pleaded guilty in July to hindering the prosecution, conspiracy and tampering with a witness and was sentenced to 1 ½-3 years in prison. Hinckley acknowledged that McDonough could have received a harsher penalty.

"But for all McDonough did, she did not rape Lizzi and she did not kill Lizzi," he said.

Hinckley said Mazzaglia sent McDonough a three-page, handwritten note detailing alibis and a plot to frame two friends for killing Marriott. He told McDonough to "rip and flush" the note. She ripped it up, but kept the shreds, which Hinckley said investigators reconstructed.

Strafford County Superior Court Judge Steven Houran denied a prosecution motion Wednesday for a mistrial. Hinckley asked for the mistrial, saying Barth had misled jurors.

Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

MORE LOCAL NEWS FROM CBS BOSTON