The trial has started in France of Jean-Marie Messier, the man who built Vivendi into a $US73 billion entertainment empire and then nearly bankrupted it.
Mr Messier is accused of misleading investors by covering up the full scale of Vivendi's debts as the company went on a massive acquisition spree.
He was sacked as chairman in 2002 after Vivendi reported massive losses and narrowly avoided bankruptcy.
Mr Messier faces a maximum sentence of five years in prison. He and six other former executives of Vivendi deny any wrongdoing.
In court, he admitted making mistakes, but argued Vivendi was really brought down by what he called a "perfect storm" of factors - the dot com crash, the terrorist attacks in the United States in 2001 and the Enron scandal.
The hearing is expected to last three weeks.