Santa Rosa police said this morning that three empty bottles of Unisom sleeping pills found next to her body in the trunk of her car indicate Stanford University student May Zhou committed suicide in January.

Sgt. Paul Henry outlined the evidence in support of the suicide conclusion at a press conference Thursday morning but he said police do not know why the 23-year-old graduate student took her life. He said no one interviewed reported her stressed or depressed and there was no indication she was pregnant.

Yitong Zhou, May's father, insisted last week his daughter was murdered and he said an autopsy in May arranged by his family in San Diego disclosed blunt force trauma to her head and extremities.

An autopsy by Dr. Kelly Arthur of the Sonoma County coroner's office found no outward signs of trauma to Zhou's body and toxicology test results determined Zhou had 6.1 milligrams per liter of diphenhydramine, the active ingredient in over-the-counter sleep medication in her system, Henry said.

Potentially toxic levels of the medication exist with dosages between 1.0 and 5.0 milligrams per liter and the effective level of the medication for most adults is between 0.1 and 1.0 milligrams per liter, Henry said.

"Preliminarily, the cause of death has been determined to be toxic levels of diphenhydramine," Henry said.

Henry said police discovered a receipt indicating May Zhou purchased Unisom L-Gel sleep medication at a Wal-Mart on Jan. 17 and again used her credit card to buy three more bottles of Unisom at three different locations Jan. 18.

Zhou was reported missing Jan. 21. Her silver Toyota Corolla was first spotted in a parking lot of Santa Rosa Junior College on Jan. 20 and remained there until Jan. 25 when it was towed to a secure facility, Henry said. Her body was then found in the trunk.

Each of the three bottles were for 32 pills and two loose blue gel pills were found in the trunk with an empty water bottle and a half-empty water bottle, Henry said.

Zhou also sent her sister an e-mail the morning of Jan. 20 shortly before she left her residence at Stanford for the last time, Henry said. A forensic psychiatrist and Santa Rosa police investigators said the message appears to be consistent with a good-bye note, Henry said. Zhou turned off her cell phone Jan. 20.

Zhou also transferred $2,000 from her $22,000 bank account to her checking account Jan. 20 and bought gas at a Valero gas station in Penryn near Auburn on Jan. 19 and at a Shell station in Palo Alto on Jan. 20, Henry said.

Henry said police are still trying to get copies of the second autopsy report from Zhou but he has refused to supply them.

"It is true that Santa Rosa police investigators have been invited to travel to San Diego to view May's body. Our position on this issue has been that a thorough autopsy examination has been completed by Dr. Kelly Arthur of the Sonoma County coroner's office," Henry said.

"At this time we have no information to contradict the findings of Dr. Arthur," Henry said. He said if provided, police will review any report that may confirm or contradict current investigative reports and investigators will travel to San Diego to continue the investigation if that is deemed helpful.

On May Zhou's Web site, Yitong Zhou said today he will exchange the second autopsy results for the results of the Sonoma County autopsy and his family still wants police to view his daughter's remains.

Henry said police are expected to complete their investigation within weeks and are waiting for one more report. He would not elaborate other than to say the report is not medically related.

— Bay City News Service

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