Updated

A prosecutor says a former SAC Capital Advisors portfolio manager got inside information about an Alzheimer's drug trial and made a pivotal phone call to his billionaire boss before the hedge fund dumped more than $700 million in pharmaceutical stocks.

Assistant U.S. Attorney Arlo Devlin-Brown made the allegation Friday during opening statements at the trial of Mathew Martoma.

Martoma was an SAC portfolio manager. Devlin-Brown said Martoma spoke with SAC Capital founder Steven A. Cohen in 2008 a day after learning secret details about Alzheimer's drug tests. The prosecutor said the firm began shedding its shares the next day.

Defense lawyer Richard Strassberg said prosecutors charged an innocent man.

Cohen has not been criminally charged but has been accused in a civil action of failing to prevent insider trading.