Determining fault is a legal issue that most police investigations do not address. When they show up at an accident site, their tasks involve: Documenting the evidence. Diagramming the accident scene. Talking to witnesses. Confirming each driver’s version. If warranted, they also test drivers for alcohol. Essentially, a police officer documents the facts. Unless an officer witnesses an accident, their report is an opinion based on evidence. Insurance companies and car accident attorneys understand this when investigating crashes and analyzing liability. Laws like California’s Vehicle Code, Division 10: Accidents and Accident Reports: §20013, prohibit police reports from becoming an issue. They prevent anyone from presenting a police report as evidence at a trial.