Insider Jury May Hear a Top Aide at Berkshire Ajit Jain, a top lieutenant at Berkshire Hathaway, is on the short list of candidates to succeed Warren E. Buffett, Berkshire's chief executive. Mr. Jain has landed on another, less desirable list: He is a potential witness in the insider-trading trial of Rajat K. Gupta. Mr. Gupta, a former director at Goldman Sachs and Procter & Gamble, faces federal criminal charges of illegally leaking information about those companies to the hedge fund manager Raj Rajaratnam, who was convicted last year of insider trading. Mr. Gupta is set to stand trial on April 9. People briefed on the case say that the defense could use Mr. Jain, a friend of Mr. Gupta, as a character witness. Mr. Jain might also describe Mr. Gupta's relationship with Mr. Rajaratnam as already having soured around the time the government asserts that crimes occurred, giving him little incentive to share inside information, these people said. Mr. Jain's role, which emerged in a pretrial conference Friday, adds to a list of prominent figures from Wall Street and corporate America who could testify in the trial in Federal District Court in Manhattan. Lloyd C. Blankfein, the chief executive of Goldman, and Gary D. Cohn, Goldman's president, are potential witnesses, as is W. James McNerney Jr., a Procter & Gamble director and the chief executive of Boeing. None of the possible witnesses are accused of wrongdoing. Goldman and Procter & Gamble spokesmen declined to comment. Berkshire representatives did not respond to requests for comment. The case against Mr. Gupta, 63, has broadened the government's sweeping insider trading crackdown beyond Wall Street trading floors and reached into some of the country's most prestigious corporate boardrooms. Prosecutors said last month that they would probably file additional criminal charges against Mr. Gupta. They have until Tuesday to file a new indictment. The collection of big-name potential witnesses in the case speaks to the vast influence Mr. Gupta once held in the business world. As the global head of the management consulting giant McKinsey & Company, Mr. Gupta, a native of India, was a trusted adviser to corporate leaders like the private equity billionaire Henry R. Kravis. He counseled leading philanthropies, working with Bill Clinton and Bill Gates on their global health initiatives. Mr. Gupta was brought low last year by the accusations that he had passed secret boardroom discussions to Mr. Rajaratnam, who used insider information to make illegal trades at his hedge fund, Galleon Group. Mr. Rajaratnam is serving an 11-year term at a federal prison in Massachusetts after a jury convicted him last May of orchestrating a vast insider-trading conspiracy. Mr. Gupta now passes the time in his waterfront mansion in Westport, Conn., and huddling with lawyers as he prepares for his trial. Several pretrial conferences in recent weeks have illuminated Mr. Gupta's defense strategy. His lawyers have suggested that the relationship between Mr. Gupta and Mr. Rajaratnam, once good friends and business associates, had deteriorated by the time prosecutors contend insider trading occurred. Gary P. Naftalis, a lawyer for Mr. Gupta, has emphasized that his client lost a $10 million investment with Mr. Rajaratnam. "We were unhappy with Rajaratnam, how he handled our investment, what kind of information he gave us, whether we were dealt with fairly," Mr. Naftalis said. Reed Brodsky, a federal prosecutor, countered that the investment losses had provided Mr. Gupta with more of a motive to tip Mr. Rajaratnam. Mr. Gupta's lawyers also suggested at another recent hearing that Mr. Rajaratnam's Galleon could have had many inside sources at either Goldman or Procter & Gamble. Prosecutors denied that there was any evidence of another informer in those companies. Mr. Jain's name came up during Friday's pretrial conference after Jed S. Rakoff, the federal district judge presiding over the case, asked for the names of possible witnesses. According to a transcript of the conference, Mr. Brodsky told the judge that both sides had interviewed Mr. Jain, and he characterized Mr. Jain as "a close friend of Gupta's." Mr. Jain, 60, has worked for Berkshire for more than two decades and oversees the company's vast insurance holdings. Mr. Buffett has long praised Mr. Jain's abilities and said that Mr. Jain would have the Berkshire board's backing if he wanted to lead the company. Mr. Gupta and Mr. Jain have similar backgrounds. Like Mr. Gupta, Mr. Jain is a native of India who graduated from Harvard Business School and was a consultant at McKinsey earlier in his career. Berkshire and Mr. Buffett already figure prominently in the government's case against Mr. Gupta. Prosecutors say that Mr. Gupta tipped Mr. Rajaratnam off about Berkshire's planned $5 billion investment in Goldman during the depths of the financial crisis in September 2008. The leak, just minutes after the bank's board approved the investment, allowed Mr. Rajaratnam to buy Goldman stock in advance of the announcement, the government contends. Another new name was disclosed as a potential witness on Friday. Judge Rakoff revealed that Claes Dahlback, a Goldman director and prominent Swedish investor, could provide testimony seen as favorable to the defense. "After Rajaratnam's arrest in late 2009, Dahlback asked Gupta if Gupta knew Rajaratnam," said Judge Rakoff, reading from a prosecution report on the case. "Gupta responded that Rajaratnam was a "bad man," and Gupta further stated that Gupta lost money with Rajaratnam." If called to testify, the Goldman and Procter & Gamble executives are likely to describe for the jury the confidential nature of boardroom discussions. In some cases, witnesses could detail their interactions with Mr. Gupta and Mr. Rajaratnam. Mr. Cohn of Goldman, for instance, might be asked about a lunch meeting he had with Mr. Rajaratnam around the time prosecutors assert information was leaked from Goldman. The lunch was referred to by Mr. Rajaratnam in a wiretapped conversation presented in evidence at his trial. Mr. Gupta's backers have mounted a public relations offensive including a Web site, Friends of Rajat, that appeared on the Internet last week. "The picture that has been painted of Rajat in the press and blogosphere contradicts what we know of Rajat first hand," reads the site's home page. Over the course of the last year, a greatly unfair and incorrect caricature of the real Rajat Gupta has emerged. Friends of Rajat solicits signatures on a letter from friends of Mr. Gupta that "fully stand by him in his cause to win back his well-deserved reputation for integrity in all aspects of his life." A number of prominent Indian-born business leaders and celebrities have signed the letter, including Deepak Chopra, the spiritual guide. The site includes quotations on justice from Desmond Tutu, Gandhi, and Elie Wiesel.