Rafael Robb, once a tenured economics professor at the University of Pennsylvania who is originally from Israel, faces a likely prison sentence of 4 1/2 to seven years for bludgeoning his wife, Ellen, on Dec. 22.
Robb, 57, said Monday that he got into an argument with his wife about a trip she was taking with their daughter and whether they would be returning in time for the daughter to return to school.
"We started a discussion about that. The discussion was tense," Robb said. "We were both anxious about it. We both got angry. At one point, Ellen pushed me. ... I just lost it."
He apologized to his 13-year-old daughter and family.
"I know she liked her mother. ... And now she doesn't have a mother," he said, stifling tears.
"It's a classic heat-of-passion killing," said Montgomery County District Attorney Bruce Castor.
Robb's attorney and prosecutors say Robb feared his wife was leaving him and would keep him away from their daughter.
Robb, who has been held without bail, spoke to his daughter by phone over the weekend and told her that he was responsible for the killing. They have not seen each other since he was arrested earlier this year.
Members of the victim's family, some in tears, sat in the courtroom Monday watching Dr. Robb on the stand describe in some detail how he killed his wife. They said they were relieved to be spared the pain of a murder trial, but angry that Ellen Gregory Robb was so brutally taken from them, reports Robin Mackintosh of CBS station KYW-TV in Philadelphia.
"She was the most amazing individual, often described as an angel on earth," said the victim's brother, Gary Gregory, "and I think that's accurate."
Robb was an expert in game theory, a complex melding of psychology, human behavior and economics - all aimed at determining what one's adversary will do next. With that background, police said, Robb probably thought he could outsmart them.
Detectives believed the scene had been staged to look like a burglary. The murder weapon - a grab-rail exercise bar that had not yet been installed, Robb said - was not found.
Ellen Gregory Robb was described as a stay-at-home mother who doted on their only child. Rafael Robb earned a Ph.D. in economics from the University of California at Los Angeles, in 1981. He had been at Penn for at least four years when the slaying occurred.
The couple had been married since 1990 but had long been estranged - keeping separate bedrooms - while living together in the house.