Affidavit describes brutality to 'Baby Grace'

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 December 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."

Ellen Robb, 49, described as a stay-at-home mother who doted on their only child, died in the kitchen of their home in Upper Merion Township, outside Philadelphia.

Detectives believed the scene had been staged to look like a burglary. The murder weapon, which Robb described as an exercise bar, was not found.

The couple married in 1990 but had long been estranged, keeping separate bedrooms.

Rafael Robb apologized to his daughter and family in court Monday.