Sarmina said the hearing Thursday would involve two witnesses: Andrea Foulkes, the city prosecutor in Williams' trial in the 1984 murder of Amos Norwood; and Marc Draper, Williams' admitted accomplice, who in new sworn statements says detectives and Foulkes ordered him to testify that Williams killed Norwood in a robbery - not in a rage over years of sexual abuse by Norwood.
In seeking clemency, Williams' attorneys have cited his youth when Norwood was killed - three months over 18, the minimum age for execution - and his sexual abuse by Norwood.
Foulkes, now a federal prosecutor in Philadelphia, has said it is inappropriate for her to comment while Williams' case is being litigated.
Draper, now 46, is serving a life sentence after pleading guilty to second-degree murder and testifying against Williams for the prosecution.
Sarmina conducted a two-hour hearing Monday on Williams' lawyers emergency motion to stay execution. She said she was skeptical but gave them until Friday to supplement their claim.
Unlike Monday, Williams, 46, was not present for Sarmina's decision, but his lawyers were pleased. If Sarmina had not stayed the execution, the hearing is the necessary prelude to block Pennsylvania's first execution in 13 years.
"It's not too much to ask for a hearing between now and Oct. 3," argued defense attorney Billy Nolas, who, with Shawn Nolan and a team from the Federal Defender's death penalty unit, represents Williams. "If we do down in flames at the hearing, we go down in flames."
Deputy District Attorney Ronald Eisenberg argued against a hearing and called Williams' purported new evidence "the same old stuff."
Eisenberg called the hearing a defense ploy "to get a stay of execution from a higher court."
Friday's hearing was one of several fronts in Williams' campaign to escape death.
On Thursday, Williams was privately interviewed by the five-member Board of Pardons about his clemency petition to have his death sentence commuted to life in prison without parole.
The board will hold a public hearing Monday in Harrisburg. It must unanimously vote for clemency for Gov. Corbett to consider the nonbinding recommendation.
In a related development Thursday, a bipartisan legislative task force studying the death penalty's efficacy asked Corbett to halt executions until the panel files its report in December 2013.
Corbett's office on Friday said the governor had sworn to uphold state law, including the death penalty: "If the governor is called upon to perform his statutory and constitutional duty, he will do so."
Williams was convicted and condemned for the June 11, 1984, killing of Norwood, 56, who was last seen leaving his Mount Airy home to volunteer at St. Luke's Episcopal Church in Germantown.
Norwood's charred body, his skull shattered by a tire iron, was found four days later in Ivy Hill Cemetery.
At issue Thursday will be the trial testimony of Draper, then 18, the son of a police officer who was arrested a month after the killing, admitted his role, and implicated Williams.
Homicide detectives said Draper told them Norwood was killed in a robbery. But in three sworn affidavits - Jan. 9, March 1 and Sept. 11 - Draper now says he told detectives and Foulkes that Norwood's killing was motivated by Williams' rage at being sexually abused by Norwood since Williams was 13.
Draper says he was told by police and the prosecutor to testify that the killing happened during a robbery and that he would have to stick to that story if he wanted Foulkes to recommend him for parole.
In arguing for the new hearing, Nolas said Sarmina Foulkes never told the jury in questioning Draper at Williams' trial that he would plead guilty and that she had promised to vouch for his cooperation.
Until this year, Nolas said, it was impossible for Williams' appellate lawyers to raise Foulkes' purported promise or Draper's statement on the real motive for Norwood's killing.
"The one thing we could never do is see inside Marc Draper's head," Nolas said.
Contact Joseph A. Slobodzian at 215-854-2985, firstname.lastname@example.org, or @joeslobo on Twitter.