Since Gregory Reyes became the first executive to be charged in the stock option backdating scandal nearly a year ago, worse transgressions have been alleged in indictments in several districts.

But as the trial of Reyes, the former CEO of Brocade Communications, began Monday morning, it became clear why his case will be a proving ground for federal prosecutors probing dozens of companies with options problems: The prosecution and defense agree that Brocade improperly accounted for the options it issued. The only argument is whether the problems amounted to criminal fraud.