Defense lawyers for the man accused of raping and killing a University of New Hampshire student say his girlfriend changed her story and testified against him only to get a reduced sentence.

Seth Mazzaglia is on trial for first-degree murder in the October 2012 death of 19-year-old Elizabeth "Lizzi" Marriott of Westborough, Massachusetts. Prosecutors say he strangled her, raped her then helped dump her body in a river.

During cross-examination, defense lawyer Joachim Barth reminded the prosecution's star witness, 20-year-old Kathryn McDonough, that she first said Marriott died during consensual rough sex with McDonough.

McDonough agreed she later changed her story, saying Mazzaglia killed Marriott after she rejected his sexual advances. She has pleaded guilty to hindering prosecution and is serving 1 1/2 to 3 years in prison.