DOVER, N.H. – Jurors who will decide the fate of the man charged with raping and killing a University of New Hampshire student were given two markedly different scenarios to weigh in closing arguments Wednesday.

Prosecutors cast Seth Mazzaglia as a cold-blooded killer who manipulated and dominated his former girlfriend and became enraged when the woman she lured to their apartment – 19-year-old Elizabeth “Lizzi” Marriott – rebuffed his sexual advances.

Defense attorneys argue that Mazzaglia’s girlfriend, Kathryn McDonough, manipulated Mazzaglia and the truth of what really happened that night to save herself. They claim McDonough suffocated Marriott during rough sex involving restraints and a panic-stricken Mazzaglia helped dispose of the body in the ocean to protect her.

Mazzaglia, 31, is charged with first-degree murder and other felonies in the Oct. 9, 2012, death of the Westborough, Massachusetts, student. Strafford County Superior Court Judge Steven Houran will instruct jurors on the law before they begin deliberating the case Thursday, after 19 days of testimony and evidence.

Both sides focused their arguments on McDonough’s credibility and her testimony over the course of 10 days.

Prosecutor Geoffrey Ward urged jurors to listen to the recording of McDonough’s grand jury testimony and her labored breathing as she spent an uninterrupted hour detailing what happened that night.

“She supplied information about the terrible things she did because she told the truth about them,” Ward said, including tying a grocery bag around Marriott’s head and pushing her body off the rocks of Portsmouth’s Peirce Island and into the ocean.

“Send him the message that you’ve seen through the lies, the cover-ups and the manipulation,” Ward said of Mazzaglia. “Know that he is a cold-blooded killer and deliver to him the justice he has for so long sought to avoid.”

Defense attorney Joachim Barth cast McDonough as a sociopath driven by voices in her head that sometimes took control of her. He claims McDonough shifted the blame to Mazzaglia during her grand jury testimony in February 2013 after being granted immunity from prosecution for any role she may have played in Marriott’s death. Barth said it greatly reduced her sentence on convictions for hindering the prosecution, witness tampering and conspiracy to 1½ to 3 years.

Barth said McDonough wanted to cover up her obsession with having dominant sex with other women “to distance herself from a truth that is very dangerous to her.”

Barth reminded jurors Wednesday that McDonough testified during the trial that days after Marriott’s death, she went to Barth’s office and gave an hours-long statement detailing how she and Marriott were having rough sex involving “breath play” and Mazzaglia was watching when Marriott had a seizure.

But McDonough also testified she was lying when she gave that account because she loved Mazzaglia and wanted to protect him. She testified that Mazzaglia strangled and raped Marriott then asked McDonough to call a friend he considered his spiritual adviser.

Before the jury Wednesday, Barth mocked McDonough’s testimony.

“In the aftermath of murdering her, he asks (McDonough) to call witnesses into the home. There is panic. Then he’s supposed to engage in this horrific sexual crime,” Barth said. “Does that make sense to you?”

Ward said Mazzaglia fantasized about dominating Marriott the night she visited their apartment, but Marriott “ruined his twisted fantasy because she has a voice and she says no.”

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