Generally under California law an owner or occupier of land owes a duty of reasonable care toward others who are on the property; a failure to exercise such reasonable care to avoid foreseeable injury can result in the owner or occupier becoming liable under the legal theory of premises liability.
Any negligence-based lawsuit will ultimately need to answer questions of actual and proximate causation among the parties involved, including whether the plaintiff was also negligent in some way. When there are multiple defendants, such as in a multi-vehicle car accident, their respective share of fault must also be allocated. How this is done brings up the issue of comparative fault.
Before former Olympic athlete then-Bruce and now-Caitlyn Jenner became known for undergoing sex change surgery, she became perhaps better known this year for a fatal multi-car accident that took place in February, in which a vehicle that Jenner was driving apparently rear-ended another car which itself had just rear-ended a third car. The impact by Jenner's vehicle apparently not only caused the original rear-end collision to happen a second time, it also allegedly sent the car that Jenner's vehicle hit into the path of a fourth vehicle, resulting in a fatal head-on collision.
There are different types of injuries that can affect the brain; the type that results from something like a car accident or a fall is known as a traumatic brain injury, or "TBI." As the name suggests, this usually results from a blow to the head. A TBI may be “open” (a severe injury which can result in a fractured or even a penetrated skull) or "closed" (such as a concussion in which the brain impacts against the inside of the skull).