The case revolves around Mr Quattrone's state of mind

The prosecution said Frank Quattrone had told his staff at CSFB to hide evidence about the bank's role in high-profile share flotations.

Mr Quattrone's lawyer argued that his client was being punished for having sent an "itty-bitty" e-mail.

"The government is asking you to connect lots of dots," John Keker said.

Both sides agree that Mr Quattrone had knowledge of investigations into CSFB when he told staff in an e-mail to clean up their records, but his defence says he intended no subterfuge.

Tough call

This is the second attempt to reach a verdict in the case.

A previous jury was unable to agree, which led the judge to declare a mistrial.

The case is seen as complex, because the arguments have revolved around Mr Quattrone's state of mind when he e-mailed his staff.

"When you get right down to it, there is only one question you have to answer," assistant US attorney David Anders told the jury.

"What was in Frank Quattrone's mind?

"Frank Quattrone knew about these investigations and knew the damage they would do to his business and his reputation."