Rafael Robb, once a tenured economics professor at the University of Pennsylvania, faces a prison sentence of no more than 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."