Until he was 5 years old, Terrell Yarbrough suckled a baby bottle. Not one that included nutritious baby formula or even cow's milk, but one filled with sugar water that caused his baby teeth to rot and fall out prematurely.

The account, told by his paternal aunt Itellia Dean, was just one of the stories conveyed to Washington County jurors as they heard testimony yesterday in the sentencing phase of Mr. Yarbrough's double murder trial.

After spending yesterday hearing from family members of the victims, an IQ expert and others, jurors this morning are expected to begin deliberating Mr. Yarbrough's fate.

On Tuesday, Mr. Yarbrough, 29, of East Liberty, was convicted of two counts of first-degree murder and conspiracy in the Memorial Day 1999 shooting deaths of Franciscan University of Steubenville students Aaron Land, 20, of Philadelphia, and Brian Muha, 18, of Westerville, Ohio.

Prosecutors are seeking the death penalty, but Mr. Yarbrough's defense team is fighting that, saying Mr. Yarbrough was a mildly retarded boy who suffered from years of neglect -- beginning in the womb -- by his heroin-addicted parents and relatives who didn't care for him.

Ohio State University psychologist Dr. David Hammer told the jury of nine women and three men that Mr. Yarbrough had dozens of IQ and developmental tests from the age of 13 that placed his IQ below 70, at which point a person is considered to be mentally retarded.

His IQ typically tested at about 59, placing him in the "mildly retarded" range, Dr. Hammer said. An average IQ is 100, he said.

Individuals in the mildly retarded range know right from wrong, he said, and can marry, obtain a driver's license and perform normal routines. More complicated tasks, such as budgeting, making quick decisions or planning, are difficult, Dr. Hammer said.

In 2002, the U.S. Supreme Court ruled that execution of the mentally retarded is a violation of the Constitution's Eighth Amendment ban on "cruel and unusual punishment."

The ruling stemmed from a case similar to Mr. Yarbrough's, in which a Virginia man was sentenced to die for a murder and robbery he committed when he was 18 years old. Like Mr. Yarbrough, that defendant's IQ was measured at 59.

County President Judge Debbie O'Dell Seneca rejected motions several months ago from Mr. Yarbrough's defense team that the death penalty be removed from consideration in his case.

Dr. Hammer said Mr. Yarbrough's scholastic record showed that he switched schools 11 times in six years as a youngster, and had "basically learned to give up" by the time he reached middle school, where he once missed 39 days in one semester.

Conversely, Mr. Land's mother, Philadelphia psychotherapist, author and grief counselor Kathleen O'Hara, said her son had an IQ of 150, could read by the age of 3, and was so smart that he skipped the first grade.

"Aaron was very special to me. I called him my sunny child," said Ms. O'Hara, who placed a framed photo of her son at her side on the witness stand.

Although her husband Howard Land died when Aaron was 14, Ms. O'Hara said her son and his siblings never used the death of their father as an excuse to act out.

"They understood that they had to go on and keep their values," she said.

Mr. Muha's brother, Yale Law School graduate Chris Muha, said his brother planned to become a doctor in underserved areas, and thought little of worldly goods, once giving away a beloved dirt bike to a less-fortunate neighbor.

On the day before he left for a summer semester at the Catholic university, which was also the day before he died, Brian Muha ordered flowers for his mother to help her get through the summer without him, said Chris Muha, who remembered hugging his brother.

"I can still feel where his arm was on my back," he told jurors.

Though Mr. Yarbrough and an accomplice, Nathan "Boo" Herring, of Steubenville, were already convicted nine years ago in Ohio of the murders, the Ohio Supreme Court ruled that the pair should be retried in Pennsylvania, where the bodies of Mr. Land and Mr. Muha were found several days after they went missing on May 31, 1999. They were accused of robbing and kidnapping the students from their off-campus apartment and driving them 20 miles into Robinson, Washington County, where they were shot to death at the top of a steep embankment.

Mr. Herring's retrial has not been scheduled yet.

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