Well, actually, it's a three step process.
It begins with the investigating officer, who would interview witnesses, and make a determination as to what the offense was and who was at fault.
Then it transgresses to the insurance adjusters, and they evaluate it according to their analysis and their documentation, and what the medical records say and what the accident report says.
Then, from there, it can go as far as to the court system, and what the judge determines as who should be apportioned fault and what percentage.
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