The lead prosecutor in the undercover sting that captured five Philadelphia legislators and a Traffic Court judge on tape accepting money will be called to testify about what role, if any, race played in the investigation, a judge has ruled.

The judge ordered former state prosecutor Frank Fina to testify in two weeks at a hearing in the case against State Rep. Louise Williams Bishop, a veteran Democratic officeholder from West Philadelphia who is charged with pocketing $1,500 in illegal cash payments.

Bishop is among six current or former Democratic elected officials from Philadelphia charged with taking money from a lobbyist turned informant who sought political and legislative favors. Four have pleaded guilty.

Prosecutors say the undercover operative gave the cash to Bishop, 82, in three meetings in 2010 and 2011. They said the informant taped Bishop replying, "That's a great help. That's a biggie," as she accepted the last payment.

Her lawyer, A. Charles Peruto Jr., has echoed contentions from state Attorney General Kathleen G. Kane that the sting may have targeted black elected officials solely because of their race.

All those charged in the case are African American.

Philadelphia District Attorney Seth Williams, who resurrected the case after Kane shut it down, has said that his office's grand jury investigation found no evidence that racial considerations tainted the probe. Williams, a Democrat, has called the suggestion of racial bias "disgusting."

Besides ruling that Fina should testify, Dauphin County Judge Scott Evans said that Claude Thomas, the sting's former case agent, also should answer questions from Peruto.

Fina and Thomas now work for Williams.

Peruto said Thursday that he hoped he would also be able to call the undercover informant, Tyron B. Ali, to testify. Evans' ruling made no mention of Ali one way or another.

Ali, 42, has never testified publicly or given an interview on his undercover role.

He became an informant as part of a deal he struck with Fina under which he escaped prosecution for allegations that he ripped off a program to feed low-income seniors and children. In September, he agreed to pay the government $63,000 to cover losses in the program.

Assistant District Attorney Mark Gilson, the lead prosecutor for all the sting cases, said that he was still reviewing the judge's ruling and that the office had not decided whether to challenge it.

Gilson added: "I've been dealing with this case for over a year now. There is absolutely no evidence of racial targeting."

He said Ali moved from target to target based on recommendations from people he knew in political circles - including legislators who took money from him.

"Four of the six people [charged] in this case have pleaded guilty," Gilson said. "Do you think for one second they would have pleaded guilty if there was a legitimate claim of racial targeting? Of course not."

Kane first raised the allegation that race played a role in the case last year. She spoke out after The Inquirer reported in early 2014 that Kane had secretly shut down the sting the previous year.

In discussing the race issue, Kane noted that of the 113 tapes secretly made by Ali, 108 were of African Americans.

She also asserted that agent Thomas told her staff that he had been instructed to go after solely black targets.

In the official assessment of the sting prepared by Kane's top deputy, Bruce Beemer wrote in 2013 that Thomas had "implied" to him that he been "instructed to focus only on the Legislative Black Caucus."

This was "shocking," Beemer wrote in the key report, and could "cripple any effective prosecution."

Thomas, who is African American, has denied ever saying that. He has said he would have protested had anyone suggested such a racial focus. He has sued Kane over her statements.

Critics of the sting have noted that Beemer also wrote that Ali had named nine lawmakers as potentially corrupt, including four whites, but that only blacks were charged.

However, Gilson said Thursday that Beemer had acknowledged to the District Attorney's Office that he erred in this section of his report, confusing Ali with a different informant. The other informant had given the list of nine names.

In testimony before a Philadelphia grand jury after Williams adopted the sting probe, Beemer said that he "never for a second" believed the racial allegation and that "absolutely nothing in the case file" reflected a racial bias.

And in an interview with Montgomery County detectives, made public recently, Beemer said he had been "upset" in 2013 when Kane suggested, in Beemer's words, that the sting "investigation was driven by racial profiling or targeting."

Beemer could not be reached for comment Thursday.

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