An April 30 hearing is scheduled on the doctors' reports on 63-year-old Leslie Gardner, of Gillette, Wyo., San Mateo County Assistant District Attorney Al Serrato said.
Criminal proceedings against Gardner remain suspended.
Prosecutors said Gardner's attorney John May expressed doubt last week about his client's ability to participate in his defense.
Gardner has pleaded not guilty to grand theft, receiving stolen property in excess of $3.2 million, and vandalism in connection with the theft of the 82-foot vessel "Darling" from the Sausalito Yacht Harbor, believed to have been taken early the morning of March 4. He is being held in San Mateo County Jail on $1 million bail.
Two other suspects, Lisa Modawell, 56, and Dario Mora, 54, both of Aptos, were also initially arrested in the case.
The couple, who were dating, met Gardner through a mutual friend in Santa Cruz, and were driven with Gardner by a fourth person to Sausalito, Serrato said.
The San Mateo County District Attorney's Office decided not to file charges against them because there was doubt about whether prosecutors could prove they knew the yacht was stolen, Serrato said.
The yacht was found when it ran aground in shallow water near Linda Mar Beach in Pacifica later the morning of the theft.
Sausalito police received a call from the yacht's owner, John Furth, of Santa Rosa, who was watching news coverage of the incident and recognized the boat as his own.
The vessel was freed and towed to Richmond for repairs.