In 1984, Teofilo Medina, Jr., stole a gun from a pawnshop in Santa Ana, California. Over the following weeks, he committed multiple armed robberies of gas stations, a drive-in dairy, and a market, during which he murdered three employees and shot at two passersby. He was apprehended less than a month after the crime spree began and charged with three counts of first-degree murder and other offenses.
Before trial, Medina's counsel moved for a competency hearing under California Penal Code section 1368, expressing uncertainty about Medina's ability to participate in the proceedings. The trial court granted the motion, and a six-day hearing was held before a jury. During the hearing, the jury heard conflicting testimony from multiple psychiatrists and psychologists regarding Medina's mental condition, including diagnoses of paranoid schizophrenia and depression, as well as observations of his verbal and physical outbursts, such as overturning the counsel table.
The trial court instructed the jury that Medina was presumed mentally competent and bore the burden of proving his incompetence by a preponderance of the evidence under California Penal Code section 1369(f). The jury found Medina competent to stand trial.
At the conclusion of the guilt phase, petitioner was found guilty of all three counts of first-degree murder and lesser offenses. A sanity hearing was held, and the jury found that petitioner was sane at the time of the offenses. At the penalty phase, the jury found that the murders were premeditated and deliberate and returned a verdict of death.
On direct appeal, the California Supreme Court affirmed the conviction and sentence. Medina later filed a habeas corpus petition in the California Supreme Court, which appointed a referee for an evidentiary hearing; the referee found Medina had been competent, and the court adopted those findings. Medina then sought federal habeas relief in the United States District Court for the Central District of California, which was denied, and the Ninth Circuit affirmed. The Supreme Court granted certiorari to address the constitutionality of the state statute allocating the burden of proof on competency to the defendant.