Witness intimidation has pervaded the Philadelphia Common Pleas Court trial of two men charged with a racially tinged double murder in the Tacony section in 2007.

Now, a brother of one of the defendants has been arrested for it.

Michael Drummond, 24, allegedly threatened a witness last week in the hallway of the city's Criminal Justice Center. Charged Saturday, he remains in custody in lieu of $250,000 bail pending a Dec. 29 hearing.

Gerald Drummond, 26, and Robert McDowell, 28, both white, face possible death sentences if convicted of first-degree murder in the July 13, 2007 slayings of Damien Holloway, 27, a black landscaper, and his friend and worker Timothy Clark, 15, who was white.

The victims were forced to kneel on the sidewalk in the 6900 block of Vandike Street and shot in the head, execution-style.

The prosecution alleges that Drummond killed Holloway because he was African American and because he had disrespected Drummond's sister, with whom Holloway had a child. Clark was killed because he was there.

Defense attorneys maintain that the defendants were elsewhere at the time of the killings.

On Monday, the witness allegedly threatened by Michael Drummond testified anyway.

Amanda Brannan, 23, spent a tense seven minutes on the stand, fighting tears, voice quiet and cracking. She told the jury she had been harassed by relatives of the two defendants because they believed her brother, Joseph, had incriminated the pair in the shooting.

"Everything was fine until they got arrested," Brannan said under questioning by Assistant District Attorney Carlos Vega.

Gerald Drummond's attorney, Michael E. Wallace, however, got Brannan to acknowledge that his client had never personally threatened her.

Witness intimidation, a serious problem in Philadelphia's criminal courts, has been a constant theme in this trial - to the point the court was cleared of spectators Friday during the testimony of one witness.

Also on Friday, Tacony resident Thomas Zehnder, 30, reluctantly affirmed his testimony from the December 2008 preliminary hearing for the two defendants. Zehnder said he overheard Drummond boast of killing Holloway and Clark at a 2007 party.

"I don't feel comfortable being here," Zehnder told Vega, explaining his hesitation. "After the last time I testified . . . the next thing I know I'm getting beaten up by half the cell block."

At that time, Zehnder was serving a prison sentence.

McDowell's former girlfriend Erica Marrero on Friday tearfully recanted a statement she made to homicide detectives in which she said McDowell told her he was present when Drummond killed Holloway and Clark.

Marrero said she had made the statement because detectives "told me I would be arrested for murder conspiracy. They told me I would never see my daughter again."

Though Vega pointed out that she signed every page of her statement and initialed each answer, Marrero insisted "it was all a lie."

Marrero said she no longer speaks to McDowell: "I'm scared, I'm scared to be here."

Her testimony led Vega to call a new prosecution witness Monday.

Susan Coulter testified after coming forward to authorities last week, saying she was motivated by a guilty conscience. Coulter said she and Marrero used to be best friends and that Marrero told her McDowell described the murders and ordered her to destroy the gun.

Coulter said Marrero told her that she dismantled the revolver and "threw the parts in the river."

Contact staff writer Joseph A. Slobodzian at 215-854-2985 or jslobodzian@phillynews.com.