You're driving down the road one-day, regular traffic conditions for 5:00pm, as you approach an intersection, the driver next to you swerves into your lane, you try and hit your brakes, but there's no time, he hits the side of your vehicle, pushes you into another lane where your narrowly miss being struck by the onslaught of traffic. After your vehicle comes to a stop and you compose yourself, you pull to the side of the road. The other driver apologizes profusely, you look at your car, there's damage to the door, but your car is still operational. The other driver kindly offers to exchange insurance cards, and even give you a picture of his ID. He then says if you call the police, they'll take an hour or two to get here, he tells you, "let's just work this out and be on our separate ways." You agree.
The next day, you wake up with a sore neck, and you make a call to the insurance company to ask where you can get treated. Much to your surprise, the insurance adjuster informs you that the other driver has changed his story. Apparently, he now thinks you are the one that tried to jump into his lane, and in doing so, hit him, and caused him to suffer injury.
Believe it or not, this story is more common than you might think. We constantly deal with drivers who modify and change their story to either attempt to escape liability completely, or limit their level of fault. Often, when drivers are friendly, apologetic, or cooperative, it causes you to lower your defenses. You don't suspect foul play, so you don't take pictures of the scene, or notice other issues, like an expired insurance card.
The scene of the crash is the first opportunity you have to lay foundation for your case. It is extremely important, that as soon as you verify everyone's well-being that the police are notified, and you take pictures of the scene.
After you have taken scene photos, its important to take additional photos of the damage to both vehicles, not just your own. You don't need to be rude to the other driver, but likewise, don't let anyone's friendly demeanor stop you from taking photos and documenting the crash while you wait for the police to arrive.
Similarly, once the police get to the scene of a crash, they typically ask each party to write their own statement of events before rendering a decision. Take time to do this. "I was driving, and the other guy hit me" is not a sufficient description. The officer will read the statements carefully as they assess liability.
As soon as you leave the scene of an accident, call an experienced attorney. They can help you open up a claim with the insurance company that will protect your interests and ensure that you get your vehicle repaired, and you get the compensation you deserve for the injuries you receive.