It is your legal right to bring a lawsuit against the police department for taking too long to finish the accident report that you have written about. However, I caution you from doing such in that from what you have written there seems to be no legal or factual basis to sue for the delay let alone establish any damages.If you file suit (where you most likely will not prevail) there is a chance under your state's statute that the police department can go after you for attorney's fees that it incurred in defending the matter that you wish to file suit over.