He said the jury could also opt to issue a detailed report documenting operative Tyron B. Ali's three years of undercover work, and recommending changes in Pennsylvania's loophole-ridden corruption laws.
Experts cautioned that Williams faces many legal hurdles as he attempts to revive the troubled probe - a key witness with a checkered past, the possible issue of entrapment, and a case already closed down and condemned by the state attorney general.
To head the new team, Williams appointed Assistant District Attorney Mark Gilson, a 27-year veteran of the office, who spent almost two decades as a homicide prosecutor.
"Because of all the controversy about this case, in the end, the citizens of Pennsylvania didn't have an answer to the most important question: Did their elected officials break the law by accepting payments for improper purposes?" Williams said. "I thought they deserved an answer to that question."
He added: "If crimes occurred here of this nature, of this magnitude, we can't stick our heads in the sand."
Williams said he had listened to some of the tapes. Asked whether he found the evidence on them convincing, he said, "It is." He did not elaborate.
In March, The Inquirer disclosed the existence of the long-running sting and that state Attorney General Kathleen G. Kane, a Democrat, had shut it down. Soon after taking office in 2013, Kane quietly ended the probe by dropping all charges against Ali in sealed court filings.
The investigation had begun under her Republican predecessor, Tom Corbett, now governor, and caught four legislators and a Traffic Court judge on tape accepting cash, money orders, or jewelry.
Kane said she ended the investigation because she believed it was poorly conceived, ineptly managed, and possibly tainted by racial targeting. All five Democrats captured on tape are African American.
She said prosecutors had let the case go stale months before she took office. According to investigative documents, Ali made his last payments on April 23, 2012 - $2,000 in cash to State Rep. Ronald G. Waters in two envelopes handed over in Waters' West Philadelphia legislative office.
Kane also criticized what she called the "deal of the century" that her predecessors had offered Ali. Under an agreement that Kane said she finally reluctantly endorsed, Ali, in return for his cooperation, had all fraud charges dropped in an alleged rip-off of a program to feed children and seniors.
In sum, Kane said, Ali was a badly tainted witness and the case he built was "not prosecutable."
Prosecutors who launched the investigation argued that Kane wrongly ended a probe that had already caught officials accepting money and that had the potential to capture more.
The sting was launched in 2010 by then-Chief Deputy Attorney General Frank G. Fina, who now works for Williams in the district attorney's new anticorruption unit. Fina is not one of the prosecutors heading the renewed investigation, a choice made to remove a possible distraction should criminal cases go forward, officials said.
The roiling controversy over the probe's fate has pitted two Democratic prosecutors, both rising political stars, against each other.
In recent months, Williams, who is black, reacted angrily to Kane's allegation that race might have played a role in the case. He also suggested she had botched a case buttressed by "hundreds of hours of devastating tapes."
He pressed Kane to turn over the sting's case file to his office, which she agreed to do in April.
Reached Wednesday, Kane spokesman J.J. Abbott said the attorney general would have no comment on Williams' announcement.
Williams said the renewed probe would be "much more expansive" than looking only at the five officeholders previously implicated in news accounts.
Still, it's unclear whether other targets are vulnerable to possible prosecution. A court filing by Ali's lawyer says Ali bestowed sports tickets, meals, drinks, and campaign donations on seven other legislators besides those already named - but those gifts appear to have been legal.
Along with heading up the new sting team, Gilson since April has been leading a special unit for the District Attorney's Office aimed at evaluating claims of people who say they were wrongly convicted.
His sting team includes Assistant District Attorneys Deborah Watson-Stokes, Andrew Notaristefano, and Brad Bender. Watson-Stokes and Notaristefano also have experience handling murder trials. Bender is in the office's Special Investigations Unit, which investigates wrongdoing by police and politicians.
Williams thanked State Police Commissioner Frank Noonan at the news conference for lending investigative support to the renewed probe - signaling that Noonan's agency, unlike Kane's office, had not washed its hands of the case. Lt. Andrew Winger, of the state police Bureau of Criminal Investigation, joined Williams and other prosecutors at the news conference.
Even before Williams took up the case, the state House Ethics Committee had launched its own inquiry, hiring Philadelphia lawyer Patrick Egan Jr. as counsel, and issuing subpoenas to Ali and for the tapes.
But Williams said Wednesday the ethics panel should hold off. "They should defer to us," Gilson agreed. "We're a criminal investigation."
State Rep. Scott Petri, the Bucks County Republican who chairs the House panel, said he could not comment on a specific probe. Speaking generally, he said, "We look at ethics violations by House members. . . . We are not charged with looking at whether there were crimes."
Could the inquiries unfold at the same time? "Probably," Petri said.
Asked about Kane's suggestion that race had figured in the handling of the case, Gilson said Wednesday the attorney general had not made public any evidence to support that charge.
Kane has said she has an affidavit in which one of her aides reported being told by a former investigator in the case that African Americans were targeted. The investigator has denied saying that.
Kane has declined to make the affidavit public, rejecting an Inquirer request filed under the state's right-to-know law. She said, in part, she could not release the document because "this investigation has now been referred to the Philadelphia County district attorney."
But Gilson said Wednesday the affidavit had not been given to city prosecutors. "I'd like to get it," he said." He said the office should be able to scrutinize all aspects of the case.
By involving the 36 grand jurors and presiding Common Pleas Court Judge Diana Anhalt, Williams said, he hoped to quell public debate about Kane's decision to drop the case and his to pursue it - and about their clash of personalities.
But in a case thought to turn largely on 400 hours of audiotape and videotape compiled over three years, some skeptics doubted whether bringing the evidence to an investigative grand jury would do much to strengthen it.
Some lawyers said they thought the use of a grand jury was designed to give Williams a face-saving "out" - he could choose not to charge anyone but instead issue a report detailing flaws in state law.
Later Wednesday, two veteran former prosecutors raised a more fundamental question: jurisdiction. Some of the alleged payoffs occurred in Harrisburg, not Philadelphia.
"So how can a Philadelphia investigative grand jury investigate alleged payments of bribes took place in another county?" asked Walter Cohen, a former acting state attorney general. "It's a really important question that they will have to address."
L. George Parry, a veteran former prosecutor, said a Philadelphia grand jury could conceivably issue a detailed report but recommend that the Dauphin County district attorney, whose turf includes Harrisburg, bring charges.
But that, too, would be complicated. Dauphin County District Attorney Ed Marsico was brought in by Kane to review the case last year, and he concluded it was too weak to prosecute, though he had not heard the tapes.
Parry said a renewed grand jury probe might produce fresh evidence. Grand juries can compel testimony from reluctant witnesses and order them to bring documents.
"It can't hurt to reinvestigate and use the grand jury to dig up more information on all the parties involved," he said, "including Ali and all the defendants."
Of course, to date there are no defendants.
Along with Waters, the other Philadelphia Democrats captured on tape were State Reps. Michelle Brownlee, Louise Williams Bishop, and Vanessa Lowery Brown - all of whom won primary renominations last month - and onetime Traffic Court Judge Thomasine Tynes.
Of the five, only Tynes has admitted accepting something of value from Ali. Tynes has said she did nothing wrong and thought wrongly that the $2,052 bracelet he gave her was a cheap knockoff.
Tynes, who is being tried on unrelated federal ticket-fixing charges, could not be reached for comment Wednesday.
Waters declined to comment Wednesday on Williams' announcement. The longtime legislator has said it was possible he accepted a birthday gift from Ali. According to investigative documents in the case, Waters pocketed the most of the five implicated Democrats - $8,250, including $1,000 at his 2011 birthday party.
Brownlee has said she could not remember whether she took money; the documents say Ali handed her $2,000 during a walk in 2011. Reached by phone Wednesday, Brownlee declined to comment and ended the call.
Bishop has denied accepting money from Ali or even knowing him. The documents say Ali gave her a total of $1,500 during three meetings - twice at her legislative office in West Philadelphia and once at a hotel on City Avenue. Lawyer A. Charles Peruto Jr., who represents Bishop, said Wednesday, "She is confident she did nothing criminal. Nothing."
Investigative documents say Brown got $5,000 in six payments. In a brief interview Wednesday in Harrisburg, she said she, too, had done nothing wrong.
This month, in an interview with WURD-AM in Philadelphia, Brown said she found news reports about her role in the sting "disheartening" while her legislative accomplishments received no coverage.
She also suggested she and others were singled out for racial reasons because, she said, it is the way she felt "justice is dealt."
"There was another representative that was not like us who had problems at the same time," she said in the interview. "And that was quickly dealt with, quietly, and it went away." She did not elaborate.