WASHINGTON — Lawyers for House Democrats on Tuesday urged a federal judge to release grand jury testimony from former special counsel Robert Mueller's investigation as Congress conducts an impeachment inquiry into President Donald Trump.

Douglas Letter, an attorney for the Judiciary Committee, said the materials are needed to investigate what Trump knew about Russia's interference in the 2016 presidential election. The committee is seeking access to grand jury witness transcripts that could demonstrate obstruction of justice, among other things.

Attorneys for the Department of Justice, however, told Chief U.S. District Judge Beryl Howell that the House Judiciary Committee has not gone through the correct legal process necessary to obtain the secret material, which was redacted in the version of Mueller's report given to Congress and released to the public.

Howell heard arguments Tuesday, but did not immediately rule on the requests.

The argument turns in part on whether the House is conducting a formal impeachment inquiry and whether it counts as a "judicial proceeding." While grand jury transcripts are secret, one exception allows them to be shared for "judicial proceedings."

Republicans argue that impeachment is not underway until a formal House vote. Democrats say no such vote is necessary, a view Howell appeared to share.

After Elizabeth Shapiro, an attorney in the DOJ's civil division, made this argument in court, the judge called the Department of Justice's position "extreme."

Letter said the Constitution affords the House complete deference on how to conduct an impeachment investigation.

"We are in an impeachment inquiry, an impeachment investigation, a formal impeachment investigation, because the House says it is," Letter said.

Shapiro then argued that "some degree of formality" should be required to pierce grand jury secrecy. When asked by Howell where that line should be drawn, the DOJ attorney said, "I'm not advocating any specific line."

"That's so not helpful," Howell said.

The discussion also turned back the clock to 1974, when Judge John Sirica, who presided over multiple Watergate cases, granted Congress access to grand jury materials as part of the House's impeachment inquiry of President Richard Nixon.

Howell asked the Department of Justice if they disagreed with that ruling. Shapiro said that the department's position has evolved since the 1970s.

"The answer would be that if that same case came today, a different result would be obtained," Shapiro said. That briefly left Judge Howell in silence.

"Wow, OK," Howell said. "As I said, the department is taking extraordinary positions in this case."

Letter also said the committee has not received FBI interview summaries, called 302s, for former White House counsel Don McGahn, a key figure in Mueller's report.

"He's an absolutely important witness," Letter said. Shapiro told the judge that the Department of Justice is in the process of redacting five 302s regarding McGahn, and that the committee would receive them soon.