Not exactly, its mostly based on state law, I know in Nebraska, as well as most states (to my knowledge) any accident involving rear end collision is the fault of the rear vechicle. If more than one is involved, it is considered a domnio effect, unless all parties state it to be otherwise or enough evidence is forund to make the officer make another decision.

And whatever an officer says goes until a judge says otherwise.

Also police reports weigh heavily on an insurance company's decision.