Last December, Economics professor Rafael Robb "lost it" during a fight with his wife, Ellen, about whether their daughter would return from an upcoming vacation in time to attend school.

That day, Dec. 22, 2006, Ellen Robb was found bludgeoned to death in the couple's Upper Merion home - a crime for which Rafael Robb admitted guilt yesterday.

Robb, 57, pleaded guilty to voluntary manslaughter in the Montgomery County Court of Common Pleas, saying he used a chin-up bar to beat to death his wife of 16 years. Robb's trial on first- and third-degree murder charges was scheduled to begin yesterday.

With the plea for voluntary manslaughter - an intentional, unjustified killing committed in a heat of passion - Robb avoided taking his chances at a trial, where a first-degree murder conviction would have carried a sentence of life in prison.

Robb also avoided the possibility of waiting in jail up to three years before a trial even began due to potential appeals by the prosecution regarding pre-trial motions.

But Robb will almost certainly still face prison time: Voluntary manslaughter carries a maximum sentence of 10 to 20 years in prison, and Montgomery County District Attorney Bruce Castor said he would ask for a "substantial" sentence above the standard guidelines of 4 1/2 to 6 years in prison.

Penn officials have spoken with Robb's lawyers, University spokeswoman Phyllis Holtzman said, and have requested Robb's immediate resignation. Defense attorney Frank DeSimone said he still needs to speak about that request with Robb, who is currently awaiting sentencing in the Montgomery County Correctional Facility.

For everyone in the courtroom, yesterday was a day for reconciling with the past and moving forward.

Robb took the stand for his plea colloquy, acknowledging, among other things, that his decision to plead guilty was his own and that he understood the rights he was giving up with the plea, such as the right to a jury trial and to present a defense.

Then, speaking softly, he explained the circumstances of the killing. Robb said he came home after taking Olivia, his daughter, to school that morning. He and Ellen both became angry as he expressed anxiety that Olivia wouldn't return from an upcoming trip with her mother before Christmas break ended.

"I just lost it," said Robb, who then grabbed the nearby chin-up bar and started waving it. "And this is what happened," he said.

Robb said he was "very remorseful" for Ellen's death, and he apologized to Ellen's family, his family and Olivia.

"I know she liked her mother," he said. "And now she doesn't have a mother."

More than a dozen friends and members of Ellen Robb's family were present in the courtroom, though Olivia was not. Many wept both as Rafael Robb spoke and as Ellen's brothers, Art and Gary Gregory, talked to reporters outside the courtroom about the family's healing process.

The family would continue to grieve for Ellen and Olivia, the brothers said. Art Gregory added that, "with a little bit of closure, we can start moving forward."

Robb's lawyers also spoke of putting the killing in the past, saying that Robb hoped he would reunite with Olivia, who is now 13, after serving his sentence.

Robb spoke with Olivia on the phone over the weekend and told her he was responsible for her mother's death, DeSimone said.

Castor said he was pleased with the guilty plea, calling Ellen Robb's death a "classic heat-of-passion killing."

"The evidence tends to support what [Robb] says," Castor added.

On the advice of his lawyers, who said they needed more time to prepare, Robb waived his right to be sentenced within 90 days. The sentencing will likely take place in about four months, DeSimone said.