In proving fault, what you're really trying to do is prove that the truck driver was negligent. Some key pieces of evidence may be witness testimony. Any witnesses from the scene of the accident, if you can interview them or if you can interview the truck driver, that can be very critical. Photographs are also very important. If you can photograph the scene of the accident, where it occurred, the vehicles involved in the accident, and the damage to the vehicles. That type of evidence can also be used to hire an expert witness, in case you need to reconstruct the accident. An expert reconstructionist may be able to go back and look at the damage to the vehicles and look at the photographs of the scene and make a determination of what may have caused the accident. Those are the types of things that you can use.