A former Citigroup executive who ran Barai Capital Management, along with a former technology expert, are expected to plead guilty to insider trading - just before Wall Street closes for the Memorial Day weekend break.  Samir Barai was charged by Federal prosecutors in February with swapping illegal stock tips with 2 portfolio managers at SAC Capital, the hedge fund run by the billionaire investor Steven A. Cohen . The 2 SAC managers - Noah Freeman, Donald Longueuil - had already pleaded guilty.   A 4th person, Jason Pflaum, an employee of Mr. Barai’s, has also pleaded guilty.

When Mr. Longueuil pleaded guilty last month, he attributed his purchase of Marvell Technology shares to a tip about the chipmaker’s financial information from Mr. Barai.  The case is connected to the government’s investigation of expert-network firms that facilitate meetings between money managers and industry experts, including employees of public companies.  A number of consultants at Primary Global Research, an expert-network firm at the center of the government’s investigation, have already pleaded guilty to providing traders with confidential information about publicly traded companies.

Mr. Barai, 39, was a former client of Primary Global.  He has been cooperating with federal prosecutors and providing them with information about his illegal trading.  The government has charged him with trading on secret corporate information provided to him by Winifred Jiau, a consultant at Primary Global.

Ms. Jiau, who has pleaded not guilty, is scheduled to go to trial on Wednesday.

    Another Guilty Plea Today.    Also Friday, Sonny Nguyen, a former employee at Nvidia, a graphics chipmaker, is expected to plead guilty to providing Ms. Jiau with confidential information about his company. He is expected to testify at Ms. Jiau’s trial.  “Nvidia placed Mr. Nguyen on administrative leave immediately upon our being informed of his intent to plead guilty, and he has now resigned,” said the company in a statement provided to DealBook. “This was a clear violation of law and our company policies. We continue to cooperate fully with the New York U.S. attorney’s office and the F.B.I.”   [NYT Dealbook, 5/27/11]