The ex-girlfriend of a man charged with raping and killing a University of New Hampshire college student left the witness stand Monday after 10 days of questioning.

Kathryn McDonough ended her testimony the way she began it: Insisting that she initially lied when she said 19-year-old Elizabeth “Lizzi” Marriott of Westborough, Massachusetts, died while the two of them were engaged in rough sex that involved restraints. She testified that her then-boyfriend, 31-year-old Seth Mazzaglia, choked Marriott after she twice rejected his sexual advances.

Mazzaglia is charged with first-degree murder. McDonough has pleaded guilty to hindering prosecution and is serving 1 1/2 to three years in prison.

McDonough said she and Mazzaglia threw Marriott’s body in a river that feeds into the ocean. Her body has never been found.

Lawyers for Mazzaglia spent a lot of their cross-examination pointing out inconsistencies between what McDonough told them at their first meeting and what she was telling the jury. Defense attorney Joachim Barth questioned McDonough extensively about whether she concocted the story blaming Mazzaglia to get years off her own sentence.

Mazzaglia was arrested Oct. 13, 2012. Two days later, McDonough told his defense team that she and Mazzaglia were both having sex with Marriott using rope restraints and breath-stopping techniques when Marriott had a seizure and died. McDonough testified at trial she concocted that story to protect Mazzaglia because she was still in love with him.

The prosecution continues its case on Tuesday.

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