As a historic Vatican financial-misconduct trial gets underway, defense lawyers are challenging the court to ensure fair treatment for their clients.

The defendants say that prosecutors have failed to comply with the court order to furnish crucial evidence—most notably the testimony of a Vatican official who was closely involved with the financial transactions that are the basis for the criminal charges.

The defense team argues that the prosecutors’ failure to provide key documents points to a broader inability of the Vatican’s court system to secure the rights of the defendants. In a court filing the defense says that the prosecution’s approach would be sanctioned “in all countries having a judicial system that could be considered autonomous and impartial and structured in a way to safeguard a fair trial.”