I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
It's never legal to file a fraudulent claim in court, and it sounds like that's what this guy is doing. But the American legal system is predicated on the belief that every person has a right to his day in court, so any person who believes himself to be aggrieved is allowed to file a lawsuit. Where there is a discrepancy as to what really happened, then it's up to the judge to decide who is telling the truth. That unfortunately means that your son will have to go to trial. He must be there to explain what happened and defend himself, even when the suit is clearly bogus.
Whenever there's a car accident, the injured driver is required to sue the other driver, NOT the insurance company, because you have to sue the person who caused your injury. That's the other driver. However, the first step if you haven't already is to contact the insurance company. They do NOT want to pay this guy $10,000, so they should provide a lawyer to help you.
In court, the other driver has the burden of proof. He has to prove both that the accident occurred and that the accident caused the damages that you're asking to have repaired. The best possible proof that your son could have is pictures of both vehicles taken immediately after the accident. If there is a police report, the officer should have indicated where the damage to the vehicle occurred, so that will also help. Unless the vehicle rolled, though, I don't see how he could possibly claim that the accident hurt EVERY surface on his truck. Your son will be able to testify as to what happened. If you have any correspondence between the driver and the insurance company (they'll give it to you), that might also help. So will whatever estimates and pictures lead the insurance company to offer $446. The goal in court is to prove that the damage he's requesting is ridiculously inflated.
He'll still get the $446 needed to repair the actual damage to the car, because he's legally entitled to have the car repaired. But your son will hopefully be able to show that the other driver is lying about the extent of the damages.
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