The Vatican’s top prosecutor has resigned, midway through the most important criminal trial in Vatican history.

Gian Piero Milano, who has held the office of “Promotor of Justice” since 2013, has stepped down, several weeks before his 75th birthday. He will be replaced by Alessandro Diddi, who has been an assistant prosecutor. Diddi has supervised the investigation that led to the trial of Cardinal Angelo Becciu and nine other defendants on financial-misconduct charges. That trial is ongoing.

The brief Vatican announcement of the change did not provide any reason why Milano stepped down before reaching the ordinary retirement age for Vatican officials, or whether his departure—and Diddi’s promotion—is related to the financial trial.