DOVER, N.H. (AP) — A woman who saw the body of a 19-year-old coed is testifying in the case of a New Hampshire man charged with raping and killing her.

Roberta Gerkin and her boyfriend were called to the Dover apartment of Seth Mazzaglia (muh-ZAYL-yuh) after the killing. Prosecutors say Gerkin cut several plastic bags from 19-year-old Elizabeth "Lizzi" Marriott's head and saw a mark on her neck.

Mazzaglia is charged with first-degree murder in the Oct. 9, 2012, death of the Massachusetts teen.

Prosecutors say Mazzaglia raped and killed Marriott after she rejected his sexual advances. His lawyers say Mazzaglia's girlfriend — Kathryn McDonough — killed Marriott during rough sex involving restraints and a choker.

McDonough is serving 1 ½ to 3 years in prison and is expected to testify against Mazzaglia.