Mr. Howe, a disgraced former lobbyist who pleaded guilty to eight felonies and is cooperating with the government, acknowledged that he tried to persuade the credit card company that he had not stayed at a Waldorf Astoria hotel, even though he had. Mr. Howe later returned to the stand and claimed that it was all just a misunderstanding. But his credibility may have been irrevocably damaged, lawyers with experience in such trials say.

“Credibility is often the key element of a trial,” said Gerald Shargel, a veteran defense lawyer not involved in the case, adding that a tried-and-true defense tactic is to undermine such credibility. And attacks on Mr. Howe, he said — who had a history of bankruptcy, theft and lies to various contractors — were so easy as to be “low-hanging fruit.”

Defense lawyers scored another victory on Monday when the judge dismissed one of the counts against Mr. Percoco, in which he was accused of extorting money from two of his co-defendants, a pair of Syracuse-area developers, in his capacity as a state official. At the time of the alleged extortion, Mr. Percoco had left his post as the governor’s executive deputy secretary to manage Mr. Cuomo’s re-election campaign.

Judge Caproni said she did not think it was extortion unless he held government office during the period in question.

Mr. Percoco, whom Mr. Cuomo once likened to a member of his family, has been accused of taking more than $300,000 in bribes from an energy company and a developer seeking deals with the state. All told, he now faces six counts, including solicitation of bribes, conspiracy and another count of extortion.