United States authorities have laid criminal charges against one of the world's biggest and most profitable hedge funds for alleged insider trading.
After a seven-year investigation, the Wall Street-based SAC Capital is being charged with four counts of securities fraud and one count of wire fraud.
Already more than a dozen current and former SAC emloyees have been implicated, although the founder, Steve Cohen, is not facing any criminal charges himself.
Prosecutors say the fund was involved in systematic insider trading, allowing it to make hundreds of millions of dollars in illegal profits between 1999 and 2010.
However, Richard Farley, a partner at New York law firm Paul Hastings, says the charges facing SAC are notoriously difficult to prove.
He says it will have to be shown that the compliance programme and the monitoring of the traders was either designed to not unveil the fraud, or that those in charge knew the illegal trading was going on and encouraged it or at least turned a blind eye to it.
He says reading the complaint carefully shows that what the government is alleging as the basis of that theory "is clearly open to alternative interpretations".
At its peak, SAC Capital managed more than $US15 billion of assets for clients.