Former Juventus Chairman Andrea Agnelli and 11 others, along with the club itself, are being examined by a judge in Turin over allegations of false accounting at Italy's most successful soccer team.
The hearing, which began on Monday, is expected to last several months, after which judge Marco Picco will decide whether to order a trial.
Prosecutors allege that Juventus understated its financial losses for three seasons, with the club denying any wrongdoing and stating that its accounting is in line with industry standards.
The case has stirred strong emotions in Italy, with Juventus' success and wealth stoking resentment from fans of rival teams.
The investigation has also triggered a separate inquiry into the club's finances by Italy's sports authority, which resulted in a 15-point deduction for Juventus this season.