Key Aide Will Appear Alongside Mueller During Hearings

WASHINGTON — Robert S. Mueller III’s longtime right-hand aide will appear beside him at the witness table during Wednesday’s hearing with the House Judiciary Committee to assist as needed as the former special counsel answers questions about his investigation, people familiar with the hearing said.

The Judiciary Committee signed off on the unusual arrangement after Mr. Mueller made a last-minute request that the aide, Aaron Zebley, be sworn in as a witness alongside him. If Democrats had agreed, lawmakers could have questioned Mr. Zebley directly, potentially upending carefully laid plans by Democrats and Republicans over how to use their scant time with Mr. Mueller.

Instead, as a counsel to Mr. Mueller, Mr. Zebley will not be under oath or theoretically allowed to answer lawmakers’ queries. But he can confer privately with Mr. Mueller, 74, if the former special counsel needs assistance or guidance about how to respond.

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It is not uncommon for government witnesses to bring aides along to congressional hearings for that purpose, though in almost all cases the aides sit behind, rather than next to, the witness. Mr. Mueller is being asked to account for two-years worth of investigative details uncovered by a large team of investigators and to do so while avoiding the disclosure of nonpublic information.

It was unclear if Mr. Mueller had made a similar request to the House Intelligence Committee, the panel holding the second of two highly anticipated hearings on Wednesday where Mr. Mueller is scheduled to testify.

Jim Popkin, a spokesman for Mr. Mueller, said on Tuesday that Mr. Zebley “will accompany special counsel Mueller to the Wednesday hearings, as was discussed with the committees more than a week ago.”

The congressional officials, who spoke on the condition of anonymity to discuss private negotiations, did not specify whether Mr. Mueller or his team explained the request.

Mr. Zebley has worked closely with Mr. Mueller for years. He worked alongside Mr. Mueller during his 22-month investigation, served as his chief of staff when Mr. Mueller was F.B.I. director and followed him into private practice at the WilmerHale law firm. He filled a similar role on the special counsel’s team, coordinating the team and serving as a go-between with the Justice Department.

Mr. Popkin identified Mr. Zebley as the investigation’s “deputy special counsel” and said he “had day-to-day oversight of the investigations conducted by the office.”

The two panels had previously expected to talk to Mr. Zebley and another former member of the special counsel’s team, James L. Quarles III, in private sessions after the public hearings. But those meetings were canceled after the Justice Department objected.

Republicans had quickly decried the possibility that Mr. Zebley could appear in public as a witness.

Representative Doug Collins of Georgia, the top Republican on the Judiciary Committee, said the last-minute addition of a witness could violate House rules. He called on Democrats to reject the request.

“If Democrats believe it is the special counsel’s responsibility to testify to his report, they have no ground for outsourcing that duty at the expense of our committee’s integrity,” he said.