More than a year after she was killed, the son of murder victim Laura Lee Robertson heard exactly how his mother died.

Tim Robertson sat in court Monday, watching a police interrogation video in which his mother's fiancé explained how he killed her and what he did with her body.

Robertson says he was tired of speculating about what had happened to his mother and needed to hear it firsthand.

"What I heard happened on that night is gross," he tells CTV News.

In the nine-hour police interrogation video, taken 12 days after Laura Robertson was killed, the accused, 33-year-old James Leopold said his fiancée died during a night of drunken sex.

"Made me angry, made me sad," says Tim Robertson. "It's like all kinds of emotions all wrapped into one. I started to shake."

Laura Robertson, 47, disappeared in April, 2011.

Her body was discovered two weeks after she was reported missing, in a wooded area in Greenfield, N.S. close to where the couple had been living.

Leopold was arrested and charged with second-degree murder shortly after her body was found.

In the video shown in court, he said Robertson intentionally bit his genitals during oral sex. He said he reacted and struck her in the neck.

"I didn't even know it was gonna happen and then it's too late, you can't take it back," says Leopold in the video. "I'm not a killer. I'm not some sick bastard who goes around killing people. This was an accident."

Leopold said Laura Robertson died instantly and didn't suffer.

In the video, he told police he put her body in bed beside him and went to sleep. The next day he wrapped her in a blanket and took her to a wooded area in Greenfield. He said he then kissed her and put tree branches around her.

"I'm very disturbed," says James Leopold Sr. "I find it very hard to accept this is what happened. He is my son and regardless of what he's done, I'll love him to pieces."

"I loved my mom, obviously, and to hear what happened to the last seconds of her life is devastating," says Tim Robertson.

The defence begins its case Tuesday. Leopold has pleaded not guilty.

With files from CTV Atlantic's Kayla Hounsell