Prosecutors ask to use tapes against Gupta US prosecutors have asked a judge to allow previously unheard recorded phone conversations to be used in the insider trading trial against Rajat Gupta, the former McKinsey director and Goldman Sachs board member. Mr Gupta has been charged with passing inside information he learnt while serving on the Goldman board to Raj Rajaratnam, founder of Galleon Group, in September 2008 and October 2008. IN Financials Mr Gupta has denied any wrongdoing. His trial is set to begin May 21. His attorney has two weeks to respond to the government's request before the judge rules. In a court filing, prosecutors said the tapes of calls between Mr Rajaratnam and his trader Ian Horowtiz are "essential evidence" of insider trading by Mr Gupta. Prosecutors have no recordings of calls between Mr Gupta and Mr Rajaratnam on either September 23 2008, when secret information about Warren Buffett's $5bn investment in Goldman was allegedly discussed before it was announced, or on October 23 2008 when Mr Gupta allegedly told Mr Rajaratnam that Goldman would report a loss for the fourth quarter when analysts were anticipating a profit. Mr Horowitz, who has not been charged with any wrongdoing, has been identified by prosecutors as an unindicted co-conspirator. To be able to use the two wiretapped calls as evidence, prosecutors need to show that Mr Horowitz is part of the conspiracy. "On the 7:09am and 7:56am calls, among other reasons, Rajaratnam needed to explain to Horowitz why other co-conspirators should not be angry that he did not share the illegal tip from Gupta with them," prosecutors said in the court filing. In the court filing, prosecutor allege Mr Horowitz's role was "reasonably foreseeable to Gupta" based on Mr Gupta's knowledge of Galleon's operations and his active role in a 2008 meeting with potential investors. On the calls, Mr Rajaratnam is heard explaining to Mr Horowitz that he had received a call at 3:58pm on September 23 and ordered Galleon traders to buy $43m of Goldman stock. Prosecutors allege Mr Gupta called Mr Rajaratnam seconds after the Goldman board meeting concluded and the board learnt of Mr Buffett's investment. Mr Rajaratnam rushed to buy shares in the final minutes of trading before Goldman announced the investment, prosecutors allege. Mr Rajaratnam was convicted of trading Goldman stock on both occasions. In one recorded call, at 7:09am on September 24, Mr Rajaratnam called Mr Horowitz and said, "I got a call at 3:58 ... saying something good might happen to Goldman." The men spoke again at 7:56am. Mr Rajaratnam expressed frustration that Mr Horowitz was not in the day before to handle the trades and he went to two other traders to execute the Goldman purchases, according to the filing. Prosecutors say the call is evidence that Mr Rajaratnam routinely shared inside information with Mr Horowitz and others at Galleon. According to the court filing, Mr Rajaratnam is recorded saying, "At 3:58, I can't, I can't yell out in the f--- halls." Mr Rajaratnam said another Galleon portfolio manager was upset adding "I've kept my mouth shut when he gave me WaMu [Washington Mutual] right?" He went on to say, "If it was, one o'clock, I am always good with him, I always call him in, I tell him everything, you know? AMD, IBM, everything, right? Mr Rajaratnam was convicted of trading shares of AMD and IBM based on inside information he received from Anil Kumar, a McKinsey partner consulting for AMD, and Danielle Chiesi, a hedge fund trader with sources at IBM. Mr Kumar and Ms Chiesi have pleaded guilty. During the calls, Mr Horowitz tried to get Mr Rajaratnam to discuss what happened on the 23rd when he was in the office but not over the phone. "We'll talk when you come in," Mr Horowitz said, according to the court filing.