Legal Question in Personal Injury in California

Am I liable?

Yes.

He doesn't have to 'give a reason' other than your were one of the registered owners. If the vehicle was insured at the time, as required by law, the insurance carrier will deal with the lawsuit. If you and your car were not insured at the time, then "tag you are it". However, 'four years later' makes little sense, so talk to your husband's attorney to see if the 'name addition' can be challenged. If he doesn't have insurance coverage or an attorney, you will need to hire one to 'fight' this case

If your husband was at fault you are liable for up to $15,000 per injured person, $30,000 per accident and $5,000 property damage.

California Vehicle Code section 17150 makes every owner of a vehicle liable for injuries or wrongful death caused by the negligence of anyone who is operating the vehicle with the permission of the registered owner. If registered in two names, each is implied to give permission to the other to drive the vehicle. A subsequent section in the same chapter limits the liability to $15,000 per injured person, $30,000 total per accident and $5,000 property damage, which happens to be the minimum legal insurance coverage required by CA law. So as you can probably see, section 17150 is an additional incentive to carry at least the minimum required insurance.