WASHINGTON — A Senate panel tried to unravel questions Tuesday about how to gather evidence for investigations despite what one senator called “the information blockade” by the presidency.

“In recent years, it has been harder and harder to get meaningful answers from the executive branch,” said Sen. Sheldon Whitehouse, D-R.I.

Lawmakers’ complaints were heightened in recent months by the refusal of Trump administration officials to testify about the former president’s role in the Jan. 6, 2021, riot at the Capitol.

Several members of his administration claimed an “absolute immunity” and “executive privilege” the Constitution and court precedents grant to members of a presidential administration.

Members of Congress disagree executive privilege is broad enough to make the presidential staff immune from liability and from subpoenas when they might have engaged in criminal behavior.

Disagreements over the extent of executive privilege prompted the Senate Judiciary’s subcommittee on Federal Courts, Oversight, Agency Action, and Federal Rights to call in the Justice Department’s top advisor on presidential authority for the hearing Tuesday.

“We need to fix this mess Mr. Schroeder,” Whitehouse told Christopher H. Schroeder, who heads the Justice Department’s Office of Legal Counsel.

When questions arise about executive privilege, the Office of Legal Counsel makes the decisions that guide Justice Department policy. If they grow into a dispute between the presidency and Congress, the Office of Legal Counsel tries to negotiate a resolution between them.

In recent years, resolution of disputes has either been elusive or too slow for lawmakers who want quick answers.

“How do we get a forum to make the case that documents are being unreasonably withheld,” Whitehouse asked.

Sen. Christopher Coons, D-Del., said “reasonableness” should determine when information is released by the president, his staff or executive agencies but added that he did not want to “tie the hands of the administration in getting anything done in the best interests of the country.”

The executive privilege doctrine is intended to free a president from risk of interference by other branches of government when carrying out the nation’s business.

Schroeder did not offer new solutions to congressional complaints. He explained how the Office of Legal Counsel performs its duties.

“We don’t call balls and strikes between an agency and Congress unless they’re making a mistake of law,” he said.

The Senate hearing coincides with mounting legal problems for Donald Trump, not only on whether he incited the Jan. 6, 2021, insurrection but also about whether he used the presidency to help his family’s real estate business.

Last week, he was subpoenaed by a House committee investigating the insurrection. On Monday, a different congressional committee released a report showing the Trump Organization would sometimes house Secret Service agents in its hotels and charge them as much as $1,185 per night.

The hotel rent was more than five times the recommended government rate for employees. Total billings to the Secret Service during the Trump presidency are likely to exceed $1.4 million, according to the House Oversight and Reform Committee report.

Eric Trump, the former president’s son, denied wrongdoing in a statement that said, “Any services rendered to the United States Secret Service or other government agencies at Trump owned properties were at their request and were either provided at cost, heavily discounted or for free. The company would have been substantially better off if hospitality services were sold to full-paying guests, however, the company did whatever it took to accommodate the agencies to ensure they were able to do their jobs at the highest levels — they are amazing men and women.”

Legal scholars generally agree Trump is unlikely to evade liability for his actions as president if they exceeded his constitutional authority.

An amicus brief filed recently by the Constitutional Accountability Center in the U.S. Court of Appeals for the District of Columbia Circuit says Trump was not fulfilling his presidential duties when he encouraged his supporters to march on the Capitol while Congress certified a win for Joe Biden in the 2020 presidential election.

The amicus — or friend of the court — brief was prepared by six law professors who were adding their opinions to a lawsuit filed by two Capitol police officers and 11 members of Congress against Trump, the Proud Boys, the Oath Keepers and Warboys. All of the plaintiffs were besieged by rioters at the Capitol.

Trump argued in his motions to dismiss the lawsuit that constitutional law and Supreme Court precedent grant him an absolute immunity that is “a key principle of separation of powers.”

The amicus curiae brief from the Constitutional Accountability Center, a nonprofit public policy foundation, agrees the president benefits from an immunity from liability but only for his official acts.

“Trump fails to point to any official responsibility that his alleged efforts to incite violence against a co-equal branch of government could have been advancing,” the amicus brief says.