Jennifer Joyce can finally tell the story of how, and why, her mother Barbara Sheehan killed her husband Raymond, the father of her two children.

"It was a huge relief," Joyce said of at last having her father out of their lives. "It sounds horrible to say that, but it was true."

Her mother Barbara is on trial for killing her husband, a former NYPD sergeant who supervised crime scenes. Her defense: that after decades of abuse she feared that day in February of 2008 that Raymond would do what he always promised -- kill her.

The prosecution, though, contends the family led a lavish lifestyle of vacations but that Barbara had grown sick of the abuse, despised her husband, and, rather than divorce him or go to police, she chose to fire 11 bullets from her husband's two guns -- killing him as he was shaving.

"I just knew. I just knew my father would kill my mother," said Joyce.

Joyce testified about the constant verbal and physical assaults her mother suffered, how the father would turn his anger on his children as well, and that when their mother intervened, the result would be a barrage of punches, kicks, slaps and other torments.

"She always had bruises on her face, her body. It was hard for me to see, and ultimately made me more afraid of my father," recalled Joyce of even her earliest years in the Sheehan's Howard Beach home.

Joyce, now a chemotherapy nurse married to a Navy pilot, refused to leave while her father was alive, choosing to commute to college, ever watchful over her mother. "I wanted to be around for my mother, protect her. But I still didn't feel like I could ultimately protect her," recalled Joyce of her years at home.

Asked about whether the family ever spoke of the violence, the rages, the bruises, Joyce quietly shook her head, saying, "I think it was just an understanding. It was like, it's bad now, but he has a gun and has told you he's going to kill you. You live with the bruises and hope you don't die."

Even after her father's death, Joyce said irrational fear lingered on. She refused to go to his funeral, but briefly went to his wake. "I had to step in and see him for myself. Because when you live with a monster like that for years I needed to see it for myself -- that he was dead."