The key evidence is your medical records. That's the most important piece of evidence in your case. For example, if you suffered a back injury in connection with an accident, then you might have an x-ray or an MRI, but you also need to show that your injuries are directly caused by the accident. For example, if you have an MRI, and all it shows is degenerative changes, that is that injuries that were caused by the body just degenerating in general and not the result of a traumatic injury, then you might be able to recover for that type of degenerative injury. However, if you can show that there was a herniation, and you can have a doctor give an opinion that they believe the herniation was directly caused by the accident, then that's the type of evidence that you need to establish your injury for damages in a car accident case.