There are circumstances where it is usually pretty clear who was at fault for the accident. For example, one driver may run a red light and be caught on camera doing so. If the driver strikes another vehicle when he ran the red, it is pretty clear who was at fault. Drunk driving crashes are another example of a situation where there is often clear evidence of who is to blame.
While these kinds of accidents with clear causes are common, they are not the only kinds of crashes that happen. In fact, it is also very common for accidents to happen where motorists disagree on who was to blame. When this occurs, making a car accident claim can become much more complicated.