The jury of seven women and five men that found the two guilty heard testimony from witnesses who described bad blood between Drummond and Holloway because of race - Drummond and McDowell are white - and because Holloway had a child with Drummond's sister.
Prosecutors said Drummond ordered Holloway and Clark to kneel on the sidewalk, hands clasped behind their heads, and told McDowell to shoot them.
When McDowell said he could not do it, Drummond took the revolver and shot the teenager in the back of the head, and Holloway in the face as he tried to run.
McDowell showed no emotion as the verdict was read. As he was escorted out of the courtroom, he turned, waved to relatives, and softly said, "Don't worry about it."
Jurors then declared Drummond guilty of first-degree murder. Drummond, dressed in a green shirt that partly hid tattoos on his hands, shook his head dismissively as the verdict was read.
The gun was never recovered, and no blood, DNA, or other forensic evidence linked McDowell and Drummond to the murders. But by September 2008, detectives testified, the men had told enough friends for them to be arrested.
A procession of those friends - mostly heroin addicts, tearful and terrorized, with criminal records - testified against the pair. Several said Drummond boasted of killing Holloway for disrespecting his sister and Clark, who also was white, because he was "a loose end."
Assistant District Attorney Carlos Vega acknowledged the criminal and drug problems of his witnesses but argued that the information they said came from Drummond and McDowell could only have been known by the killers. Vega said his witnesses' shaky bearing was caused by fear of retaliation from the Drummond and McDowell families.
One of Drummond's brothers, Michael, 24, was charged with intimidating a trial witness last week in a courthouse hallway. He is in custody pending a preliminary hearing on Dec. 29. Other witnesses described intimidation by Drummond's older brother, David, 28, or McDowell's sister, Tara, 25, who is married to Gerald Drummond and the mother of his two children.
Vega said the penalty hearing was delayed because "it would not be fair to the jury" to keep them in court during the holiday season. That hearing is expected to last at least two days.
Family members of the two victims were escorted out of the courthouse by police.
Defense attorneys Gary Server, for McDowell, and Michael E. Wallace, for Drummond, said they would offer mitigating evidence in an attempt to keep their clients off death row.
Contact staff writer Nathan Gorenstein at 215-854-2797 or firstname.lastname@example.org.