Over the last half-decade, as federal authorities secured dozens of insider trading convictions against hedge fund traders, they have tried doggedly to build a case against one of Wall Street’s most influential players: the billionaire stock picker Steven A. Cohen.

On Tuesday, the government appeared to inch closer to that goal. Prosecutors brought charges against a former portfolio manager at the hedge fund SAC Capital Advisors in a case that for the first time directly involves Mr. Cohen, the fund’s founder.

Mathew Martoma, a former portfolio manager at CR Intrinsic, a unit of SAC, was charged with making more than $276 million in a combination of illegal profits and avoided losses by obtaining secret information from a doctor about clinical trials for an Alzheimer’s drug being developed by the companies Elan and Wyeth.  Read more