A PORTRAIT of Sabina Rose O'Donnell's alleged killer emerged in a Philadelphia courtroom Monday as a forensic psychologist explained the conclusions from a battery of tests he administered to Donte Johnson, who is on trial in the 2010 rape and murder of the Northern Liberties waitress.

Gerald Cooke, the final defense witness, who was paid more than $9,300 in taxpayer money for his services, testified via video recorded last week that Johnson, 20, was likely born withbrain damage, the origin of which is unknown. His mother was 16 when he was born, and his father factored little in his life due to being in and out of jail, Cooke said.

Cooke, who runs a private practice, said Johnson's brain impairment has resulted in an IQ lower than 96 percent of the general population, speech and learning disabilities, a personality disorder and the ability to function intellectually no higher than an 11-year-old.

Also, Cooke said, Johnson's brain damage has been made worse by his abuse of marijuana and hard alcohol. He has never held a job, dropped out of high school after ninth grade, had been arrested three times before being charged with murder but still managed to have "lots of girlfriends," Cooke said his investigation of Johnson revealed.

With Cooke's testimony, defense attorney Gary Server and co-counsel Lee Mandell are trying to convince the Common Pleas jury that Johnson could not have "knowingly and voluntarily" given the police statement in which he confessed to raping and murdering O'Donnell.

The 20-year-old's nude, battered and strangled remains were found early on June 2, 2010 in a lot behind the 4th Street and Girard Avenue apartment building where she lived with her stepfather, Mark Rounds.

If convicted of first-degree murder, he would receive a mandatory life sentence with no parole.

The defense and the prosecution team of Assistant District Attorneys Richard Sax and Gwenn Cujdik are scheduled to make closing arguments Tuesday. Court was cut short Monday due to a power outage on some floors at the Criminal Justice Center.

Before the prosecutors rested their case earlier in the day, they called to the witness stand Rounds — who testified about the last time he spoke with his stepdaughter and about identifying her remains — and the victim's best friend, Marie Alyse Rodriguez.

Rodriguez was among the friends with whom O'Donnell went to a restaurant on the evening of June 1, she recalled. Rodriguez said O'Donnell later accompanied her to her apartment to watch movies. Tearfully, she said that after she had fallen asleep on the couch, O'Donnell woke her up about 1 a.m. June 2 to ask if she could borrow her bicycle to ride home. O'Donnell was murdered shortly after arriving at her building.

O'Donnell often stayed over and would have done so that night, Rodriguez said, if it had not been for her bed being so cluttered with clothing. n

Mensah M. Dean, contact him at 215-568-8278 or deanm@philly.com.