Jerome Kerviel, a former trader at Socit Gnrale, who was sentenced to three years in prison in 2010 after being convicted of unauthorised computer use, forgery and breach of trust, has begun an appeal hearing.
As well as the prison sentence, Kerviel was also fined an unprecedented 4.9 billion (£4.3 billion) and banned for life from trading.
The trader, who has an advanced knowledge of IT after having previously worked in Socit Gnrale's IT department, had circumvented the bank's security controls and made a series of unauthorised transactions, costing the bank 4.9 billion euros (£4 billion) in 2008.
According to the BBC, Kerviel has denied responsibility for the bank's huge loss at the hearing, and said that his bosses knew what he was doing. They were happy with his actions until he made the loss, he claimed.
"I am not responsible for this loss and the acts I am accused of," he said at the hearing in Paris.
"I always acted with the knowledge of my hierarchy."
The hearing is due to take place throughout June.
French regulators fined Socit Gnrale 4 million euros for failures in its internal risk management systems following the scandal.
The bank spent 130 million between 2008 and 2009 to strengthen its systems and controls. But in August 2010, it was fined £1.6 million by the UK Financial Services Authority for failures that meant it was inaccurately reporting four in every five of its transactions.