BRENTWOOD, N.H. — A New Hampshire woman charged with lying to investigators about her whereabouts the day a University of New Hampshire student was killed is scheduled to enter a guilty plea and be sentenced next week.

Prosecutors say 19-year-old Kathryn McDonough lied when she told investigators she had no contact with Elizabeth “Lizzi” Marriott on Oct. 9 — the day they say the UNH student was strangled or suffocated. Prosecutors say McDonough also gave a false alibi for her and the man charged with killing Marriott, Seth Mazzaglia.

Court records say McDonough is scheduled for the plea hearing and sentencing in Rockingham County Superior Court on July 25. She’s charged with witness tampering, hindering prosecution and conspiracy to hinder prosecution.

The body of 19-year-old Marriott of Westborough, Mass., has not been found.

Prosecutor Peter Hinckley declined to comment on the case Tuesday.

Mazzaglia, 30, has a July 31 scheduled appearance in the Rockingham court.

Mazzaglia says Marriott’s death was an accident during a night of consensual sex that also involved McDonough. He told investigators he and McDonough used Marriott’s car to take her body to Peirce Island in Portsmouth, where they threw it and her cellphone into the Piscataqua River.

Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.