WASHINGTON — The prosecution rested its case on Wednesday in the trial of Stephen K. Bannon, a former top adviser to President Donald J. Trump, as government lawyers sought to show that Mr. Bannon had repeatedly ignored warnings that he risked facing criminal charges in flouting a subpoena.
Mr. Bannon was indicted in November on two counts of contempt of Congress after he refused to provide information to the House committee investigating the Jan. 6 attack.
The trial on Wednesday largely centered on the testimony of Kristin Amerling, the deputy staff director and chief counsel to the Jan. 6 committee, who offered a detailed accounting of the committee’s attempts to compel Mr. Bannon to testify last year.
“There had been a number of public reports stating that Mr. Bannon had been in communication with White House officials, including former President Trump in the weeks leading up to the Jan. 6 events,” Ms. Amerling said. “We wanted to understand what he could tell us about the connection between any of these events.”
Prosecutors continued to describe Mr. Bannon’s decision to stonewall the committee as a straightforward case of contempt. By declining to testify, Mr. Bannon not only “thumbed his nose” at the law, but he also may have withheld significant information about the coordinated effort to disrupt the certification of the 2020 election, Amanda Vaughn, a prosecutor, said.
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During questioning, Ms. Amerling told the court that Mr. Bannon would not acquiesce to the committee’s requests for emails and other documents even after receiving a letter threatening legal action.
Mr. Bannon never asked that the deadline for the subpoena be extended, nor did the committee consider his claim of executive privilege to be valid, Ms. Amerling added.
The committee has repeatedly identified Mr. Bannon as the architect of a plan to sow doubt that either Mr. Trump or Joseph R. Biden Jr. had amassed enough electoral votes to win the election, creating a scenario in which the House would then have had to decide the outcome.
On cross-examination, M. Evan Corcoran, a lawyer for Mr. Bannon, sought to paint the indictment as nakedly political, and, he appeared to suggest, driven by the whims of Representative Bennie Thompson, Democrat of Mississippi, the committee’s chairman.
The defense pointed to a July letter, in which Mr. Thompson seemed open to hearing testimony from Mr. Bannon, provided that he also supplied the committee with documents it had requested. The letter lent credence to Mr. Bannon’s claims, his lawyers said, that his dealings with the committee were open-ended and that he had never formally ruled out speaking with committee members.
In his questioning, Mr. Corcoran appeared intent on portraying Ms. Amerling as a political operative, pressing her for details about her career working for Democrats on various congressional committees and her past political donations.
He also grilled Ms. Amerling about a book club she has attended in which another prosecutor in the case is also a member.
The prosecution objected to the efforts by Mr. Bannon’s lawyers to inject politics into the proceedings. Before testimony even began on Wednesday, the judge in the case, Carl J. Nichols, warned the defense against asking witnesses to speak to the motives of specific members of Congress.
“I do not intend for this to become a political case, a political circus, a forum for partisan politics,” the judge said.
Prosecutors also called Stephen Hart, an F.B.I. special agent, as a second witness. Mr. Hart, who had met with Mr. Bannon’s former lawyer about the subpoena last year, presented social media posts in which Mr. Bannon appeared to celebrate his decision to flout the subpoena.
Mr. Hart’s testimony appeared to contradict the argument Mr. Bannon’s lawyers have made that at that time, and even in recent months, Mr. Bannon believed he and the committee were still negotiating over a deadline for his cooperation.
The trial against Mr. Bannon began this week after a series of rulings significantly limited his defenses.
His lawyers had offered a number of reasons that Mr. Bannon had declined to testify before Congress, only for Judge Nichols to systematically reject them.
Notably, Judge Nichols dismissed the idea that Mr. Bannon could claim executive privilege conferred by Mr. Trump shielded him from the subpoena. He also declined the defense’s request to delay the trial until October over concerns that high-profile news coverage of the House committee’s public hearings this summer could prejudice jurors.
The defense will have an opportunity to present its side on Thursday. It is unclear if Mr. Bannon or any other witnesses will testify, and the case could conclude as early as this week.