Find one of the parties broke a law.

I am basing this on Idaho laws but most states are the same.

1.Following Too closey, if it’s a rear end this always applies
2. Too fast for conditions, you could be going to 2 miles an hour but if you slide on ice you were going to fast for conditions.

I have never seen an accident where someone didn’t do something that could result in a ticket and in some counties here in Idaho(Ada county in particular) it is policy the officers have to issue a ticket if they can determine someone did one of those things in an accident