Every case must be evaluated on its own merits. How the case should be investigated is determined on a case-by-case basis. In a serious truck accident, ideally, you would want to be able to get to the scene while it is still fresh and photograph the evidence before it can disappear. You would also want to have a professional download the electronic data from the electronic data recorder or black box as it is known colloquially. This information can be very valuable in establishing the location, route, driving distance, speed, and other details that can be important to understand what led to the crash.