In a cautionary move, federal prosecutors have deployed a “filter team— in the trial of former House aide and lobbyist Kevin Ring, who is charged in the ongoing influence-peddling investigation of disgraced ex-lobbyist Jack Abramoff.

According to several former prosecutors knowledgeable with Justice Department practices, it is not unusual to employ two teams of prosecutors — sometimes referred to as “clean— and “dirty,— or “filter,— teams — to sort through evidence in white-collar criminal cases.

“It’s a smart idea. Basically what it is, is you have prosecutors who are not the trial prosecutors sift through the evidence,— said Loyola Law School professor Laurie Levenson, a former assistant U.S. attorney in Los Angeles.

Levenson explained the dirty team reviews evidence, such as that obtained in searches, to remove any privileged materials like documents that may be protected by the attorney-client relationship.

“You want to do that because if trial prosecutors are exposed it may compromise your case,— she added. Prosecutors are prevented from using such materials, or any information derived from those documents or statements, against defendants.

Steve Bunnell, a partner at O’Melveny & Myers and former chief of the criminal division of the U.S. Attorney’s Office for the District of Columbia, noted that filter teams may also review materials that could fall under the Constitutions’ Speech or Debate Clause, which protects Members from prosecution for actions related to their legislative duties.

“The filter team is basically a way to make sure the lawyers who are actually trying the case are not exposed to evidence that would taint them in some way,— Bunnell said.

Filter teams are more likely to be used to screen for Speech or Debate materials in the wake of the 2006 raid on then-Rep. William Jefferson’s (D-La.) House office, which the Supreme Court agreed in 2008 had violated the constitutional protection.

In that instance, FBI agents raided Jefferson’s office, and the agency utilized a filter team to screen out documents that appeared to be legislative materials.

But Jefferson argued that because he was not granted the opportunity to assert privilege over documents related to legislative activity before the raid, the FBI had violated his Speech or Debate protections. The U.S. Circuit Court of Appeals for the District of Columbia ruled in his favor, and the Supreme Court later denied an appeal from the Justice Department.

“People want to make sure their cases are more secure,— said Citizens for Responsibility and Ethics in Washington Executive Director Melanie Sloan.

It remains unknown what exactly the filter team in Ring’s case is examining, although District Judge Ellen Huvelle indicated at a status hearing in late June that the team may be examining documents that could lead attorneys to invoke the attorney-client privilege.

“I thought that I was given this [information] because … your filter team was concerned about attorney client communications,— Huvelle said, according to a transcript from the hearing.

According to court documents, federal prosecutors asked the judge in a private filing submitted in April to review potential evidence — identified only as “Exhibits A, B and C— — and rule on whether it is privileged information.

Federal investigators seized a variety of items in their investigation of Ring, including e-mails from his former employer, Greenberg Traurig, as well as materials taken during a May 2008 search of his Kensington, Md., home.

A search warrant indicates federal investigators could seize materials related to an autobiographical book being drafted by Ring, including “any and all drafts, outlines, or notes of other books, memoirs, biographies, or any other compilation relating to Kevin Ring’s employment with Jack Abramoff.—

According to federal prosecutors, the draft book included discussions between Ring and his attorney, Richard Hibey, a possible point of contention.

A July 16 letter addressed to Huvelle and reprinted in court records indicates the filter team includes U.S. Attorney for the District of Maryland Rod Rosenstein and Assistant U.S. Attorney Mara Zusman.

At Huvelle’s request, an attorney representing the filter team is expected to appear in court next month for the next status hearing.

Ring, a one-time aide to then-Rep. John Doolittle (R-Calif.) who later worked with Abramoff on K Street, is charged with bribery and conspiracy to commit fraud. He is scheduled to go on trial in the U.S. District Court for the District of Columbia in September. He has denied wrongdoing.