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Marriott was a sophomore marine biology major at the University of New Hampshire (UNH) in 2012. She lived with her aunt in Chester, New Hampshire, and that city's authorities are investigating her case. She attended an evening chemistry class on October 9 and was last seen at 9:00 p.m. that day in Durham, New Hampshire near the hospital. Marriott sent a text message to a friend at 8:55 p.m., saying she was going to visit someone named Kat and then go home. She was driving a tan 2001 Mazda Tribute with the New Hampshire license plate number 304-5397 at the time; a photo of a similar vehicle is posted below this case summary. She has never been heard from again. Her vehicle was later recovered in a parking lot at the UNH campus on Mast Road in Durham.
On October 13, Seth J. Mazzaglia was charged with Marriott's murder. In December, Kathryn "Kat" McDonough was charged with hindering apprehension and conspiracy to commit the same in connection with the case. She is Mazzaglia's girlfriend and had worked together with Marriott at Target. Photos of McDonough and Mazzaglia are posted below this case summary.
In July 2013, McDonough pleaded guilty to all the charges against her and agreed to testify against Mazzaglia. At his trial in June 2014, she spent ten days on the witness stand. Mazzaglia's defense attorney argued it was McDonough, not Mazzaglia, who had killed Marriott by accidentally suffocating her during sex. The prosecution argued Mazzaglia had intentionally strangled and raped Marriott because she'd resisted his advances. Mazzaglia was convicted of first-degree murder and sentenced to life in prison. Later, he was sentenced to an additional three and a half to seven years because he'd attempted to escape from jail while awaiting trial.
Marriott's body has never been found and investigators believe it was washed out to sea.
Left: Tan 2001 Mazda Tribute;
Center: Kathryn McDonough;
Right: Seth Mazzaglia