In his final defence, Kerviel's lawyers, described the accused as humble "young Breton", passionate about banking and economics who was corrupted by Société Générale, a pawn in a global frenzy for profit and called for him to be cleared of all charges.
"Jérôme Kerviel is not a fraudster. He was trained, formed by Société Générale, deformed if you will," said the defence lawyer Olivier Metzner, adding: "Jérôme Kerviel is the creation of Société Générale."
Metzner, a heavyweight at the French bar, asked: "Who are you Société Générale?", echoing the question "Who is Jérôme Kerviel? asked by the judge Dominique Pauthe at the start of the trial.
Metzner concluded that Kerviel was being made a scapegoat for the global financial meltdown.
"When everyone is winning, nobody minds. When everyone loses, there has to be someone – just one – found guilty," he said before sitting down.
Metzner called for him to be acquitted on charges of abuse of confidence, computer hacking and falsification of records.
Kerviel had admitted making unauthorized bets on the stock market; at one point he was trading €50bn, more than the bank was worth. But he insisted his bosses knew what he was doing and encouraged him to take risks in pursuit of profits. The bank denied this and accused him of being a "manipulator, a trickster and a liar" who caused a "planetary trauma" that almost brought down one of France's oldest banks. Asked by the judge at the end of the trial if he had anything further to add, Kerviel said he did not.
Kerviel joined Société Générale in 2000 in its back office, but was promoted to the trading floor in 2005. In his first trading year, he made the bank €5m, rising to €12m the following year. In 2007 he made €1.5bn, but declared only €55m of this hoping to carry the rest over to the following year.
Most of his extraordinary gains were made through speculative deals which he claims traders knew were not officially allowed but were tolerated as long as they turned a profit. But in January 2008 Kerviel's complex web of hidden deals began to unravel when Société Générale discovered he was involved in trades worth about €50bn more than the bank's market value. In selling off Kerviel's trades over a three day period when the global markets were dropping, the French bank lost €4.9bn.
The court will announce its judgment on 5 October, said Pauthe. If found guilty Kerviel faces a five-year sentence – one year suspended – and a €375,000 fine. The bank has claimed €4.9bn it lost in damages.