If you are rear-ended and forced to hit the car ahead of you who is responsible in California?

The vehicle behind you.

Even though your car made contact with the front vehicle, if you're forced into the front vehicle, you can't be held liable.

The adjusters who investigate liability on this claim will definitely want to get the statement of that front driver, because liability essentially hinges on what he or she says. If, for instance, the front driver says he felt just one "bump," it means the middle vehicle was pushed into him. If he says he felt two "bumps," it generally means the middle vehicle rear-ended the front vehicle, bounced off, and was then pushed back into the middle vehicle by the rear vehicle. (This isn't always true, however, because some collisions are hard enough that a middle vehicle can bounce back and forth).