A year after being handed the case by the Senate, the Justice Department continues to investigate the improper accessing of more than 4,600 Democratic memos from the Judiciary Committee by a pair of former GOP staffers.

No indictments have been handed down and the case appears to have slowed to a near halt since the holidays. But U.S. Attorney David Kelley had previously interviewed at least 20 current and former Republican aides as well as Senate Sergeant-at-Arms Bill Pickle and a team of Secret Service agents Pickle used to conduct the chamber’s internal investigation into the memo case, according to more than a half-dozen individuals with knowledge of the probe. A few former Democratic staffers were also questioned, sources said.

The probe, according to those who have spoken with investigators, is focusing on the actions of Manuel Miranda, the former Judiciary staffer who also worked for Majority Leader Bill Frist (R-Tenn.). Last fall Miranda filed a civil suit in a long-shot bid to convince a federal judge to shut down the investigation, a bid that the judge rejected in a scathing opinion only two weeks later. Miranda’s appeal of the ruling is now before a federal appellate court.

In seeking dismissal of that civil suit, Justice Department lawyers indicated that a grand jury had been impaneled, citing the grand-jury secrecy rule, 6(e). But the interviews with staff appear to have been done on a voluntary basis, rather than through compelled testimony before a grand jury, and here in Washington.

A Justice spokesman declined to specify if a grand jury was looking into the case, or elaborate further on any details of the investigation, citing its ongoing nature. “There is a criminal investigation but no charges have been brought to date,” said the spokesman, Kevin Madden.

Senate Minority Whip Dick Durbin (D-Ill.), whose Judiciary staff files were targeted more than those of any other Senator, said he has grown a little anxious about the case because he has received no update on the investigation, which was sparked a year ago this week when he and other panel members sent the Pickle report to the Justice Department and requested a formal probe.

“They have not spoken to me. I think it would be appropriate at this time for me to write him and ask for a general status update,” Durbin said last week. A letter, from Durbin and Sen. Patrick Leahy (D-Vt.), Judiciary’s ranking member, could go out to Kelley as early as this week.

Pickle, who conducted a six-month investigation into Miranda’s actions at the behest of Senate leadership and the Judiciary Committee, said last week that he and the Secret Service detailees he used for the internal probe are not helping Kelley with his criminal investigation. Pickle and his Secret Service agents were interviewed by Kelley and are considered witnesses in this case, as were some aides to top Republicans such as Frist and Republican Conference Chairman Rick Santorum (Pa.).

Pickle cited the request of the Senate Legal Counsel that he not discuss the details of the case, declining to say what he told Kelley, who is the acting U.S. attorney for the Southern District of New York, based in Manhattan.

“They have interviewed many of us up here, as you would expect,” he said. Kelley was given a copy of the 67-page report that Pickle compiled, as well as other investigative material, although it’s unclear how much information Senate counsel allowed the investigators access to, given the sensitive nature of the separation of powers issues at the heart of the case.

In his report, Pickle determined that during an 18-month period, from late 2001 into early 2003, Miranda and a junior Judiciary staffer, Jason Lundell, accessed at least 4,670 documents from a computer server that was left without safeguards. Only a few of the documents were from Republicans, and the report portrayed Miranda as the leader of the effort in which he instructed Lundell to look through the Democratic files.

Pickle’s report outlined a handful of possible criminal violations, including making false statements to federal agents. That crime would apply to any false statement made to the Secret Service detailees.

Miranda, who declined to comment for this story, has long maintained his innocence in the case, saying there was no illegal “hacking” in the case since the files and memos weren’t protected. He has likened himself to a whistleblower, exposing the ties Judiciary Democrats had to outside liberal activists on the contentious issue of judicial nominations.

Lundell’s lawyer, Robert Driscoll, also declined to comment on the case.

The memo case came to light — and set off a firestorm on the committee — when The Wall Street Journal’s editorial page excerpted some highlights of the memos in November 2003, and when a small conservative interest group, Coalition for a Fair Judiciary, later posted 14 of the memos on its Web site.

Soon after, Miranda — who had moved to Frist’s staff from Judiciary in early 2003 — and Lundell left the Senate.

While Pickle’s internal probe had no power to subpoena any statements or documents from groups outside of the Senate, Kelley has that power and should be able to determine how the documents ended up in the public arena.

After Kelley personally reached out to her, Kay Daly, the founder of the Coalition for a Fair Judiciary, has since declined to comment on her dealings with the federal prosecutor, citing her lawyer’s advice. Sean Rushton, executive director of the Committee for Justice and a close friend of Miranda’s, also declined to discuss his talks with Kelley because of the prosecutor’s ongoing investigation.

Frist said he has not been briefed by Justice about the investigation and declined to comment on how many of his staffers had to be interviewed by investigators.

Santorum said one of his aides, who he declined to name, was interviewed in the fall. “That was a while ago, months ago,” he said. “It’s sort of fallen off the radar screen. I assumed not much was happening. But who knows, these investigations can take time.”

Aides who have been questioned by Kelley or his investigators have had the assistance of Senate Legal Counsel, although no other staff beyond Miranda and Lundell are considered potential targets in the case.

After officially receiving the case last April, Kelley conducted the bulk of the interviews in the fall and early winter, according to those familiar with the talks. Sources could not point to a single interview conducted in the past two months, leaving the future of the case unclear.