The Niigata court opened his trial on May 23, 2000. In the proceedings, the prosecutors acted very carefully to avoid further damage to Sano's mental health. The prosecution's case included even minor charges against Satō (for example, shoplifting of women's underwear) with the goal of putting him in jail for as long as possible. Following a defense claim of criminal insanity, on September 6, 2001, psychiatrists found Satō to be mentally fit to face the charges, and he subsequently admitted the main charges. In the first instance, on January 22, 2002, the Niigata District court sentenced him to 14 years out of a maximum of 15 years.