A French court is due to announce its verdict in the case of former Societe Generale bank trader Jerome Kerviel.
Mr Kerviel stood trial earlier this year over allegations that he bet 50bn euros ($69bn; £43bn) of SocGen's money without the bank's knowledge.
The bank claimed his actions cost it about 5bn euros.
Mr Kerviel's defence was the bank knew about the risk-taking and was content while he was making profit.
The prosecutor in the trial has called for Mr Kerviel to spend four years in prison, if convicted.
He was charged with forgery, breach of trust and unauthorised computer use and the maximum sentence for the allegations is five years.
The trial saw Mr Kerviel's former bosses and colleagues line up to testify against him.
SocGen's lawyer, Jean Veil, accused Mr Kerviel of "duplicity" for reassuring his bosses that nothing was wrong while racking up the huge losses.
And the bank's president and chief executive at the time of the losses, Daniel Bouton, called the trading scandal a "catastrophe".
But Mr Kerviel's lawyers argued that the failure was more than incompetence, and that there was a culture of rule breaking at SocGen where management deliberately turned a blind eye in the hunt for profit.
The bank was fined 4m euros by French regulators for failures in those systems following the scandal.
The Kerviel affair has dealt a blow to reputation of one of France's most prestigious financial institutions, said BBC business reporter Mark Gregory, but added that in some respects the fall-out had been less than might be expected.
Our correspondent says this is due to the timing.
Jerome Kerviel's dealings are now often seen as footnote to the much larger global financial panic that followed the collapse of the US investment bank Lehman Brothers a few months later, he says.
The few billion dollars lost by SocGen pale besides the hundreds of billions of dollars thrown away through risky dealings in America's sub-prime mortgage market, our correspondent adds.