DOVER, N.H. (CBS/AP) — A jury on Friday convicted a 31-year-old man of killing and raping a University of New Hampshire college student following a trial filled with lurid details of sexual domination, experimentation and violence.

The jury in Strafford Superior Court found Seth Mazzaglia guilty of first-degree murder in the death of 19-year-old Elizabeth “Lizzi” Marriott of Westborough, Massachusetts, in October 2012.

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The key witness, 20-year-old Kathryn McDonough, was Mazzaglia’s girlfriend when she lured Marriott to their apartment. She testified that Mazzaglia wanted another woman to join their sexual escapades, which included bondage and discipline.

McDonough first told investigators that Marriott died during rough sex between the two women that involved restraints. After getting immunity from prosecution, McDonough changed her story and said Mazzaglia strangled Marriott then raped her. After Marriott was dead, Mazzaglia and McDonough dumped her body in river. It has never been found.

Mazzaglia was found guilty of one count of first-degree murder that stated he strangled Marriott “before, after or while” sexually assaulting her. He also was convicted of conspiracy to falsify evidence and conspiracy to tamper with witnesses.

Mazzaglia showed no emotion as the verdict was read. He was led from the courtroom in handcuffs.

He will be sentenced to life in prison without the chance of parole.

Marriott’s father, Bob, said the family is grateful for the verdict but that even a life sentence will never soothe their grief. Marriott gave a police officer a bear hug after the verdicts were read.

“We will always miss her and we wonder what could have been,” Marriott said, his voice quavering. “In fact, the trial has been torturous for us. The truth of what happened to Lizzi is horrendous. And every time it’s been told, it has reinforced the despair that we feel.”

Marriott said the verdict will keep a dangerous man off the streets and protect other women.

He also had harsh words for Mazzaglia’s lawyers for what he called intentionally misstating his daughter’s action the night she died.

“Blaming a victim who is unable to defend herself is a typical ploy used by defense teams. If you are dead, you cannot correct a mischaracterization,” he said.

Mazzaglia’s lawyers did not comment after the verdict.

Jurors began deliberating Thursday, after hearing 19 days of testimony. McDonough was on the stand for 10 of those days.

The trial hinged on McDonough’s credibility. Mazzaglia did not testify.

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“She had told so many lies, she was a pathological liar,” Juror Maria Clifford told WBZ-TV. “But at the point she started to testify she wanted to set the record straight.”

Clifford believes Mazzaglia was domineering and controlling of McDonough, but on the stand she was free to speak her mind.

“Even though she did horrendous things she owned up to it,” Clifford said. “That was what brought me personally to the fact that I think she was telling the truth.”

McDonough initially told investigators that she killed Marriott during consensual sex but later said she made that story because she loved Mazzaglia, thought they still had a future together and wanted to protect him.

Defense lawyers, though, painted her as an opportunistic liar who killed Marriott then changed her story when she found out she could cut a deal and get less time in prison if she pinned the crime on her ex-boyfriend.

The deal was conditioned on her testifying truthfully.

In court, she testified that Mazzaglia was the sexually dominant partner in their relationship and became angry when she left for nearly two weeks at theater camp without recruiting a sex partner for him. As what she called punishment, Mazzaglia told her to lure a woman — Marriott — to the apartment on Oct. 9, 2012.

After a game of strip poker which prosecutors say Marriott willingly joined, Mazzaglia suggested she kiss McDonough. Marriott said no, saying she was in a committed relationship. Mazzaglia then asked if she would watch as he and McDonough had sex. She again said no.

Prosecutors said Mazzaglia was unaccustomed to being rejected so, as the two women watched a movie, he sneaked up behind Marriott and choked her with a rope. McDonough testified that she left the room briefly and when she returned, found Mazzaglia raping Marriott’s limp body.

Mazzaglia’s lawyers said McDonough, who pleaded guilty to hindering prosecution and is spending 1 ½ to 3 years in prison, was interested in experimenting with women and initiated the sexual activity that night in the apartment she shared with Mazzaglia.

Maria Clifford says the jury was unanimous from the start during eight hours of deliberations. She hopes the verdict will comfort the Marriott family.

“Hopefully they’re comforted by the fact he’s behind bars and will not do this to somebody else,” Clifford said.

WBZ-TV’s Beth Germano contributed to this report.

(TM and © Copyright 2014 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2014 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)

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