Once a car accident occurs, law enforcement authorities arrive on the scene and start to gather evidence for their investigation. Over days or weeks, these authorities put together a version of what has occurred to cause the accident. If someone has hired attorneys, attorneys will usually hire their own private investigators to investigate the causes of an accident. Both law enforcement and investigators will usually look to the same sources to find answers:

1) Witnesses. Anyone who saw the accident occurred may be interviewed about what they saw. Witnesses may include emergency response personnel called to the scene of an accident to tend to personal injuries, passers-by, drivers in other vehicles on the scene, and anyone else who may have seen the accident.

2) Investigating weather and road conditions. Investigators will usually look at weather reports in the area, reports of city work and construction work ordered for the area, and witness reports of weather and road conditions in the area that may have contributed to the accident.

3) Expert witnesses. Expert witnesses may not have been at the scene of an accident, but have specialized knowledge which is admissible in court about factors that affected an accident. For example, a mechanic may be interviewed to explain about the specific flaws in a car model, if a products liability issue may be part of the accident investigation.

4) Medical records. Medical records can help determine whether a driver’s medical condition contributed to an accident. A victim’s medical records from the emergency room and subsequent doctor’s visits can help investigators gauge the seriousness of the injuries and how they might have been sustained in the accident.

5) Background checks. Investigators will often run background checks to check the employment and driving history of a driver or victim. If a driver has previous drunk driving convictions and shows signs of being intoxicated, for example, this can be an important clue for investigators.

6) Mechanical investigations. Investigators will often have a vehicle carefully tested to see how it responds in normal driving conditions. This can help determine whether a product defect has contributed to an accident. A mechanic can also investigate the types of damages a car has sustained to determine what must have happened during the crash to cause the specific type of damage. This can help determine what occurred during an accident.

7) Accident reconstruction. Investigators have access to accident reconstruction software, which allows investigators to create an accurate step-by-step video of what happened during an accident. This can help investigators prove what occurred and what led to the accident.