WASHINGTON — A key witness in the federal criminal trial of Roger J. Stone Jr. testified on Thursday that Mr. Stone had misrepresented him to congressional investigators in 2017 as his intermediary with WikiLeaks even though he had repeatedly urged Mr. Stone to “tell the truth.”
The testimony of Randy Credico, a New York radio host, seemed to bolster the prosecution’s contention that Mr. Stone, a former Trump campaign aide, had deliberately lied in his testimony to the House Intelligence Committee in September 2017. At the time, the committee was investigating Russian interference in the 2016 presidential election, including the role of WikiLeaks.
But the radio host’s credibility remains an issue in Mr. Stone’s trial, now in its third day in a federal courthouse in Washington. Mr. Stone, a 40-year friend of President Trump, has been charged with obstruction of justice, making false statements and tampering with a witness in what prosecutors claim was an effort to shield Mr. Trump and his campaign.
Prosecutors warned jurors this week that Mr. Credico was a less than perfect witness. On the stand, he acknowledged that at points in late 2016, he had exaggerated his relationship with Julian Assange, the founder of WikiLeaks, to Mr. Stone.
At the time, Mr. Stone was trying to reach Mr. Assange to obtain information about tens of thousands of emails that Russian intelligence operatives had stolen from Democratic computers and funneled to WikiLeaks in an effort to hurt Hillary Clinton, Mr. Trump’s political opponent.
Mr. Credico also acknowledged that he had abused alcohol off and on for 34 years, although he said he had been sober for the past year. He came to the courtroom without his “therapy dog,” who accompanied him to the courthouse for his grand jury testimony.
The trial of Mr. Stone, 67, has revived the story of the Trump campaign’s efforts to benefit from Russian interference in the 2016 race just as an impeachment inquiry has riveted the nation’s attention on whether Mr. Trump tried to pressure a foreign ally to bolster his 2020 re-election chances. His case is one of three prosecutions of former Trump aides by the special counsel, Robert S. Mueller III, that are not yet resolved.
A Republican consultant known for political trickery, Mr. Stone is accused of deceiving investigators from the House Intelligence Committee about his efforts to contact WikiLeaks and his discussions with senior Trump campaign officials. He is also charged with trying to prevent Mr. Credico from cooperating with congressional investigators and Mr. Mueller’s team.
Mr. Credico, who describes himself as a comedian and an impressionist, delivered vivid, entertaining testimony, sprinkled with references to television, movie and political characters. Describing his long battle with alcohol, he insisted that he was not like Otis Campbell, the town drunk on “The Andy Griffith Show,” a television hit decades ago.
When Judge Amy Berman Jackson said he was “a little mumbly” and should speak up, Mr. Credico said he felt like Mumbles, a villain in the old “Dick Tracy” comic strip. “Let me know if I do it again,” he told her.
At another point, he broke into a brief, convincing impression of Senator Bernie Sanders, the Democratic presidential candidate. “We know you are a comedian, but this is serious business,” the judge chided him.
Mr. Credico described a long, rocky friendship with Mr. Stone. In 2011, at a low point in their relationship, he said, Mr. Stone posted messages on social media reporting that he had died of a drug overdose. That “caused some problems” with family members and friends, Mr. Credico said dryly.
Text messages and emails between the two men, introduced into evidence, are laced with profanity and insults. In one text, Mr. Stone referred to Mr. Credico as “Rummy,” a reference to his drinking problems. Yet they also helped each other professionally. Mr. Credico said Mr. Stone was an excellent guest on his radio show.
Although the trial only began on Tuesday, Mr. Stone’s lead defense lawyer, Bruce S. Rogow, appears to be struggling. When he announced that he was not going to cite page or exhibit numbers while questioning an F.B.I. agent, Judge Jackson instructed him to do so.
After Mr. Rogow concluded a ponderous, sometimes confusing cross-examination, the judge waited until the jurors had left the courtroom, then told him that he had “tested the patience of the jury a great deal.”
Zach Montague contributed reporting.