Now that Brian Hall has confessed to a 20-year-old murder, he'd like us to assure him that the crime wasn't all that bad.

Just as his trial was about to begin yesterday, Hall took the unusual step - in a highly unusual case - of admitting to a Common Pleas jury that he killed Rosella Atkinson in a field next to Central High's football field in October 1987.

He wants the jury to decide whether the slaying amounted to first-degree murder, as the commonwealth contends, or a lesser offense.

The proceeding, known as a degree-of-guilt hearing, will be conducted like a trial, ending with jurors deliberating among first-degree murder, third-degree murder, voluntary manslaughter or involuntary manslaughter.

"There's only one issue, one single issue: What is his mental state at the time that he committed the killing?" defense attorney Helen Levin said to jurors during her opening remarks. The only "relevant evidence," she said, would come from Hall's 2005 confession to homicide detectives.

In that confession, Hall told cops that he had taken Atkinson, an 18-year old mother whom he described as a "party girl," to the field at Broad Street and Somerville Avenue to have sex. He can't remember if they did anything because he blacked out. When he awoke, he discovered money missing from his sock, he said.

"I put my hands around her neck," he said.

According to prosecutor MK Feeney, Hall "choked the life out of her."

He covered the corpse with twigs and debris and left her in the field to rot, Feeney said.

Miles Pettiford, a teen tossing a football around in that field, found her skeletal remains in February 1988.

"I can't remember exactly how I felt, but I knew that it was a body," he testified yesterday.

Police could not identify the bones Pettiford found, so the medical examiner's office - which had determined that the case was a homicide - handed the cranium over to forensic sculptor Frank Bender.

Bender was known for creating lifelike busts that showed what fugitives would look like as they aged and for giving life and expression to what had only been bones.

One of his most famous busts showed the aging of fugitive John List. List was apprehended in 1989, 18 years after he killed his family.

The bust of Rosella Atkinson, Bender said yesterday, was shown on TV and in the newspapers as frequently as List's had been.

Yet no one had identified the young woman's remains for years, until Atkinson's great-aunt, Lois Brown, went to a Bender art exhibit at the

Mutter Museum in Center City.

"I looked at the bust in the paper and I didn't really recognize it," Brown testified yesterday. "I walked to the Mutter Museum . . . I went back to that bust that was in the paper. I kept going back to the bust.

"Then it hit me that I began to see the bone structure of that face," she said. "I saw my mother and my sister, which was Rosella's grandmother. And I was convinced that was her."

She called Atkinson's mother, Freedeina Carney.

"I took my kids," Carney said of her visit to the museum.

"We looked and we studied [the bust] and we looked at it, and it hit us all at the same time and we just broke down and cried because we could see her. It looked like her."

Dental records confirmed the horrifying suspicion. But even after the bones had a name, the killer's identity remained a mystery.

It seemed to be a cold case with no hope of being solved. But in September 2005, Hall, plagued by guilt, went to police and confessed.

"My conscience is eating me, and I know it's time to get it right," he said at the time. "I had to come clean because I see her face a lot of times and I just want to do what's right."

He told homicide Detective Aaron Booker that he hadn't meant to kill the girl. He couldn't even remember her name. He just needed "closure."

"His demeanor was pretty matter-of-fact," Booker testified. "He just wanted to get it off his mind. He was pretty cool, calm and collected, and pretty sure about the information he was giving.

"Relief is how I would describe it."

The jury is expected to begin deliberating tomorrow. *