When a confidential document leaked into the public sphere last week, it revealed the Justice Department is seeking to trump a House ethics investigation of Rep. Alan Mollohan (D-W.Va.). While the request offered no new insight into the Mollohan inquiry, it did shine light on the often murky relationship between House ethics officials and federal prosecutors.

The request, included in a confidential ethics committee report obtained by the Washington Post, is typical in cases in which the DOJ is engaged in its own investigation.

According to individuals familiar with the process, the working relationship between the Justice Department and the Committee on Standards of Official Conduct, commonly known as the ethics committee, is usually a cordial one, although tensions do flare.

“The conversations between Justice and the committee are difficult and strained at times because each entity has a legitimate interest in carrying out its responsibilities,— said a source familiar with the ethics committee who asked not to be identified because of the sensitive nature of the panel’s work.

“But the potential for either side, the ethics committee or the Justice Department, to inadvertently undermine the work of the other is real,— the source added.

The Justice Department and the House ethics committee operate under confidential strictures and rarely discuss their probes publicly, but former Congressional aides and ex-DOJ officials acknowledge the agencies do communicate with each other about investigations.

Rather than providing each other with regular updates, sources said, one office typically contacts the other in response to news reports about an investigation or when a witness discloses contact with investigators.

“It’s very situation-specific,— the source familiar with the ethics committee said. “Hypothetically, you can imagine that the FBI or Justice Department officials are pursuing leads or interviewing witnesses, and in the course of doing that, a witness might tell them, ‘As I explained to the House ethics committee …’ and the Justice Department investigators, at that point, they would know.—

The Justice Department’s Office of Legislative Affairs typically handles contact between the ethics committee and the agency — organizing meetings that could include House aides and the DOJ’s Public Integrity Section, which prosecutes public corruption cases. The Attorney General’s Office is sometimes employed.

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, said the DOJ often intercedes in an investigation because of concerns about the “fact-gathering process.—

“One of the things you don’t want in an investigation is to have key witnesses being interviewed multiple times by different people,— Bunnell said, noting that such a process could result in multiple versions of testimony, a potential weakness in a federal prosecution.

While the Justice Department usually reaches out to the ethics panel in the early stages of such an investigation, Bunnell noted one major exception: a probe in which the DOJ employs wiretaps or other covert operations.

“They probably don’t want to ask the ethics committee to stand down because they don’t want to tip off the subject of an investigation,— he said.

But in a typical scenario, when the DOJ and the ethics panel are investigating identical or even related charges, Justice officials essentially request the House to “stand down,— he said.

While neither the DOJ nor the ethics committee can ultimately force the other to forgo an investigation — such a scenario would violate the Constitution’s separation of powers — sources said the House generally defers to the Justice Department.

“Most of the time ethics will defer to Justice because you don’t want to be in the position of impeding a criminal investigation,— said one former Congressional aide, who asked not to be identified in order to discuss the ethics process.

Although the House can also ask DOJ officials to suspend their efforts, sources said the majority of requests flow from the Justice Department to Capitol Hill.

Nonetheless, even when the House agrees to postpone its work, the ethics committee may continue to pursue elements of the case.

“There may be a potential House ethics violation that can be separate from a criminal investigation,— the former Congressional aide said.

In mid-September, the ethics committee disclosed that it was deferring action on an investigation of Rep. Jesse Jackson Jr. (D-Ill.) at the request of the Justice Department.

According to a statement issued at that time, the committee indicated at least a portion of the investigation — a referral from the Office of Congressional Ethics — could remain active.

“The Committee will continue to monitor the situation and will consider pursuing avenues of inquiry that it concludes do not interfere with the activities of the Department of Justice,— Chairwoman Zoe Lofgren (D-Calif.) and ranking member Jo Bonner (R-Ala.) wrote. “The Committee reserves the right to assert its jurisdiction if, in its determination, a violation of House rules, code, or other laws under its jurisdiction are discovered that will not interfere with the Department of Justice’s activities.—

The investigation is focused on Jackson’s ties to disgraced ex-Gov. Rod Blagojevich (D), who is accused by federal investigators of choreographing a pay-to-play scheme to auction an open Illinois Senate seat in late 2008.

In addition, the OCE, which reviews potential rules violations and recommends investigations to the ethics committee, had reviewed whether Jackson used his taxpayer-funded office budget, known as a Members’ Representational Allowance, to promote his interest in the Senate seat, a potential rules violation.

It is not known what elements of that referral, if any, the House ethics committee is still investigating.

But while parallel investigations may occur, Bunnell noted that the two agencies — which sometimes informally request evidence from one another — would never conduct a joint investigation.

“One thing the Justice Department has historically and continues to be very careful about, is they do not want to become ‘partners’ in an investigation with any Congressional committee,— Bunnell said, adding it would raise separation of powers issues.

Still, the Justice Department can turn over information to the ethics committee in an investigation, although it typically defers doing so until it has completed its own work or determined it cannot pursue a criminal prosecution.

“If you want the fruits of Justice’s work, you’ll most likely have to wait until DOJ has wrapped up its case to get them,— said the source knowledgeable of the ethics committee.

Several sources pointed to the example of the ethics committee’s proceedings that ultimately led to the expulsion of Rep. James Traficant (D-Ohio) in 2002, a few months after his conviction in federal court on 10 felony counts of bribery, racketeering, fraud, obstruction of justice and tax evasion.

But even when such an outcome is possible, sources familiar with the House ethics panel said deferring any investigation often creates image problems, drawing criticism from government watchdogs who demand action and delaying potential outcomes of an investigation.

“Justice doesn’t exactly keep you posted on what they’re doing, and they often move very slowly,— the former Congressional aide said. “They were not very forthcoming on their time frame. You couldn’t hold a potential ethics investigation in abeyance forever.—

“If they wouldn’t tell us where they were in the investigation, we might say the committee will move forward if we didn’t hear anything else from Justice,— the former aide added.

In one notable instance, the ethics panel in 1998 halted its probe of then-Rep. Bud Shuster (R-Pa.) at the request of the Justice Department, then reignited the investigation six months later.

The ethics committee ultimately declared in 2000 that Shuster brought discredit on the House and slapped him with a “letter of reproval,— a minor punishment.

Although the confidential ethics committee report obtained by the Post also indicated that at least seven lawmakers are under investigation for their ties to now-defunct lobby firm PMA Group, it is not clear whether the Justice Department has attempted to intervene in that ethics inquiry.

FBI agents raided PMA’s office in November 2008, reportedly as part of an investigation into improper campaign contributions.

PMA employees and clients were leading donors to Reps. John Murtha (D-Pa.), Peter Visclosky (D-Ind.), Jim Moran (D-Va.), Norm Dicks (D-Wash.) and other appropriators, and received multiple earmarks from these and other Members.

In addition, Visclosky announced in May that his offices and aides had been subpoenaed by federal investigators examining the Indiana lawmaker’s relationship with PMA.