House Judiciary Chairman Jerrold Nadler filed a petition in federal court Friday to obtain secret grand jury material underlying former special counsel Robert Mueller’s report, arguing the panel needs the information as it weighs whether to pursue impeachment of President Donald Trump.

The panel is also expected to file a lawsuit next week to try to enforce a subpoena against former White House counsel Donald McGahn, a key Mueller witness, if he doesn’t comply before then.

The Judiciary committee’s filing says the panel needs the information in order to determine whether to recommend articles of impeachment, partly an attempt to give the request more weight in the eyes of the court.The move comes after Mueller’s testimony Wednesday to Congress saying he had not “exculpated” Trump.

Democrats are trying to focus public attention on Mueller’s words and on his 448-page report’s contents, including several episodes in which Trump sought to influence the special counsel’s investigation into Russia election interference.

That suit is expected to challenge the White House’s claim that former White House employees have “absolute immunity” from testifying before Congress.The committee’s court battles are beginning as the House leaves for a six-week recess and Democrats are debating whether to impeach the Republican president.

Around 100 House Democrats have said they favor starting the impeachment process, but House Speaker Nancy Pelosi has said she wants to build the strongest case possible before making that decision, including by going to court to force witnesses to comply.

Mueller concluded that he could not exonerate Trump on obstruction of justice. He also concluded that there was no evidence of a criminal conspiracy between Trump’s campaign and Russia.

Nadler said ahead of the court filing that the grand jury information “is critically important for our ability to examine witnesses” like McGahn and for them to investigate the president.

It’s unclear what new information might be found in the grand jury transcripts. Many of the high-profile witnesses connected to the White House, for instance, appeared for voluntary questioning before Mueller’s team rather than before the grand jury.