The manufacturers of a self-driving car can be held and are held liable today, same as if the brakes were defective (strict product liability) or improperly marketed (negligence). That doesn't mean the driver might not also be liable. It all depends on why an accident occurred and a host of other factors. There's really nothing special about self-driving cars in this respect, except that litigation can be much more factually complicated. For failing breaks, it's relatively clear given X speed and Y distance, and assuming they were engaged, whether they worked. Then you work backwards from there. Negligent driving? Poor maintenance (driver or mechanic)? Defective design? But in driver assistance and automation systems there are many more questions about what was actually expected to happen, or what was reasonable to expect to happen.