Insurance adjusters determine who is at fault in a car accident and may assign a percentage to each driver. The amount of compensation is directly affected by the legal definition of negligence in the state where the accident occurred and the percentage the adjuster assigns to each party. Insurance companies will often dispute liability in order to deny or reduce a claim. 

As such, it is crucial to contact the authorities immediately after an accident. When police respond to an accident, they may write a police report or accident report which may include information about the parties, the conditions surrounding the accident and conclusions about the cause of the accident and who was at fault. A police report, along with witness testimony and other physical evidence such as photographs and videos, may ultimately resolve the issue of liability and fault.