Determining fault following an auto accident involves deciding who was the negligent or careless party. In most cases, common sense dictates who was at fault. There is usually one person who clearly violated traffic regulations or failed to yield the right of way. If there is official support of a claim to back up a story after an accident, the argument is strengthened for the insurance company. When trying to prove the other party was at fault, there are several places to look for the necessary supporting evidence.

Police Reports
If police responded to the accident, there will be a police report. They almost always respond if they suspect there are injuries or if they are contacted. Contact the traffic division at the police department to ask how to obtain a copy of the report. In some cases, the police report will have a statement from an officer about his or her opinion or observation. This may include who the officer knew or thought was at fault. If the other party is listed, this is helpful to include with the insurance claim. The officer may issue a citation to the other party for violating a traffic regulation, and this can also be helpful to include. Whether the police report is brief or detailed, any mention of the other party's negligence is useful.

Traffic Laws
Every state has its own publication of traffic laws. Look for the laws, and find ones that support the evidence of the other driver being negligent. State statutes outline these rules, and they are normally called vehicle codes. Most DMV offices also have booklets that contain simplified explanations of these laws, so that is a good place to look as well. Public libraries and law libraries normally have copies of the entire vehicle code, and they are published in one or more places online.

In the vehicle code index, search for listings that are related to the accident. Look for specific but applicable topics such as right of way, speed limits or road signs. Librarians can help find these in a law library. Be sure to make copies of any laws that apply to the incident. While the DMV publications are useful for explaining the laws in simpler terms, it is better to have the actual vehicle code and citation handy when presenting an argument that the other party is at fault.

No-Doubt Liability
In certain types of accidents, the insurance company will assume fault with the other driver almost 100 percent of the time. Rear-end collisions are one typical example. One universal rule of driving throughout the country states that drivers should maintain a safe distance behind another vehicle to allow ample time to stop. If someone hits another vehicle from behind, the insurer will assume that person was following too close or not paying attention. Also, the telltale signs of a rear-end collision are the damages to the front of the responsible vehicle and the damages to the back of the vehicle that was hit.

Only in a few cases will comparative negligence play a part and reduce the compensation of the person who was hit. For example, a brake light that was out could make it harder for someone to see when a car is slowing down. Another common example is a vehicle turning left. If there is a collision with a vehicle coming from the opposite direction, the turning vehicle is almost always at fault. To learn more about this topic, discuss concerns with an agent.