Question: Is my friend liable for the DUI too? He was an underage passenger (20) in a car of a girl who was arrested for DUI in Studio City, CA.

Answer: I do not think that your friend will be looking at any charges based on what you wrote, but of course, there may be more to the story. If criminal charges are filed against your friend, then I would recommend hiring an attorney to handle them. Was your friend cited for any violation regarding this matter yet?
Phil Hache,
Criminal Defense & DUI Attorney
Handling DUI and Criminal matters throughout Courts in Southern California including Van Nuys, CA, San Fernando, CA, Burbank, CA Glendale, CA Pasadena, CA Metropolitan Court, Bellflower, CA, Alhambra, CA, Malibu, CA, Compton, CA, Santa Clarita, CA, Airport Court, Chatsworth, CA Inglewood, CA, Los Angeles, CA and other Courts