When a defendant relies on a “diminished actuality” defense, the People are not entitled under Penal Code section 1054 (discovery in criminal cases), to access to defendant for purposes of a mental examination conducted by a prosecution expert. Petitioner was charged with premeditated murder and other felony crimes resulting from the assault of his wife and daughter. When petitioner stated his intent to rely on a “diminished actuality” defense, the prosecution claimed that because petitioner placed his mental state in issue, it was entitled to have the court order petitioner to submit to a mental examination by a prosecution expert. The trial court granted the prosecution’s request. Disagreeing, the Supreme Court determined that a mental examination is discovery subject to the criminal discovery statute, Penal Code section 1054, enacted following the passage of Proposition 115. Interpreting the statute, the Court found that it does not authorize a trial court to issue an order granting access to a defendant for a prosecution expert examination when a defendant places his mental state in issue. (Rejecting several pre-Proposition 115 holdings to the contrary.) Further, although the discovery statue permits discovery if authorized by some other “express statutory provision,” the Court found no other statute authorizes prosecution discovery in this situation. The Court declined to consider whether Evidence Code section 730 provided the authority as the prosecution had not preserved the issue for appeal. It rejected the prosecution’s claim that discovery was authorized under Penal Code section 1054.4 which provides for non-testimonial discovery, finding that a mental examination is testimonial evidence. Although the discovery statute permits discovery if mandated by the United States Constitution, the Court rejected the prosecution’s claim that there is no constitutional impediment to the discovery sought, pointing out that the statute specifically permitted discovery “mandated” and that there is nothing in the Constitution mandating such discovery. Lastly, the Court rejected the prosecution’s claim that denying access violated the People’s right to due process under the California Constitution. The court directed the trial court’s order be vacated, but suggested that the prosecution was free to seek access to defendant under the authority of Evidence Code 730.