Steven A. Cohen's SAC Capital Advisors LP is at the center ofthe biggest insider case ever filed in a sweeping U.S. crackdown onillicit hedge fund trading — one that focuses on the burgeoningexploitation of secret information on volatile health carestocks.

In doing so, the new case against a former Cohen lieutenant hasbrought the five year probe beyond the realm of technology stocksand into the busy underworld of health care industry securitiesfraud. The charges against former SAC portfolio manager MathewMartoma also place U.S. prosecutors closer than ever to Cohen, thehedge fund's billionaire owner and founder, in the broadest probeof insider trading in a generation.

Martoma, 38, was accused by prosecutors in Manhattan federalcourt with playing a lead role in what they called the mostlucrative insider-trading scheme in history, given the $276 millionprofit he allegedly helped the hedge fund achieve. Martomaparticipated in trading on insider tips about clinical trials of adrug to treat Alzheimer's disease, the U.S. said, and advised Cohento sell shares of Wyeth LLC and Elan Corp. before bad news aboutits prospects was announced. The government referred to the“hedge-fund owner” in court papers.