Eric Nungaray, of San Jose, is facing charges of driving under the influence of alcohol and drugs and causing injury, and driving under the influence of alcohol with a blood alcohol level of .08 percent and causing injury.
He will plead to the charges on Wednesday.
The crash occurred at about 3:15 a.m. Sunday on the shoulder of northbound Highway 101 just north of Metcalf Road.
The occupants of two cars, a Mitsubishi and a Toyota, were on the shoulder tending to a flat tire on the Toyota when Nungaray, driving a Mercedes, veered off the roadway and crashed into the rear of the Mitsubishi.
The impact pushed the Mitsubishi forward into the Toyota, severing the leg of a 23-year-old San Jose woman who was standing between the two cars.
The driver of the Toyota, a 23-year-old Morgan Hill man, suffered major head injuries.
Both were transported to San Jose Regional Medical Center.
The driver of the Mitsubishi, a 29-year-old Milpitas man who had stopped to assist with the flat tire, suffered major head injuries and internal bleeding and was transported to Santa Clara Valley Medical Center.
Nungaray was treated at Valley Medical Center for a fractured ankle and other moderate injuries before he was booked into Santa Clara County's main jail.