DOVER, N.H. — Jurors in the murder trial of a man charged with raping and strangling a 19-year-old University of New Hampshire student got to see two sides of the state’s star witness on Wednesday.

Defense lawyers played an hourlong videotape of then-18-year-old Kathryn McDonough reviewing a statement in which she said she caused the death of 19-year-old Elizabeth “Lizzi” Marriott during rough sex on Oct. 9, 2012. McDonough is a former girlfriend of 31-year-old Seth Mazzaglia, who is charged with first-degree murder.

The video was made a week after Marriott died and two days after McDonough told defense investigators that Marriott, of Westborough, Massachusetts, had a seizure and stopped breathing during sex with McDonough involving restraints.

McDonough shifted blame for the killing to Mazzaglia after being granted immunity from prosecution. She testified last week that Mazzaglia strangled Marriott with a rope after she twice rejected his sexual advances and then raped her as she lay motionless on the floor.

Jurors had in front of them on Wednesday McDonough on the witness stand watching McDonough projected on a large screen. They will ultimately decide which McDonough to believe.

The video depicts a relaxed McDonough reading a typed version of the detailed statement she gave to defense attorney Joachim Barth and his investigators two days after Mazzaglia’s arrest. Occasionally she makes corrections or elaborates when an investigator asks questions.

When the video was over, Barth questioned McDonough about the contrast in her stories and demeanor when questioned about the night Marriott died at the Dover apartment she shared with Mazzaglia.

McDonough said the story she told his office on Oct. 15, 2012, was “a very big lie.”

“I created the lie two days before,” she said.

Testimony opened Wednesday with two FBI forensics experts saying strands of hair found on an island in Portsmouth where prosecutors say the couple dragged Marriott’s body before throwing it in a river probably came from Marriott.

After the forensic experts’ brief testimony, McDonough returned to the stand for a seventh day of testimony.

McDonough and Mazzaglia admitted they used Marriott’s car to transport her body, which they then dumped into a river that flows into the ocean. The body has not been recovered.

Barth questioned how, if McDonough had witnessed Mazzaglia kill and rape Marriott, she could continue for months to profess her love for him and write that she felt safe with him. Barth pointed out how that contrasted with her grand jury testimony last year that she was afraid that if she had tried to stop Mazzaglia from killing Marriott he would have killed her as well.

“Even when he was the one murdering someone, I couldn’t run away from him,” she replied. “I didn’t want to lose him.”

Barth has hammered home through four days of cross-examination that McDonough repeatedly lied to police, Mazzaglia and defense investigators until she cut a deal.

McDonough said Wednesday that she was protecting Mazzaglia previously, but now “this is the truth.”