Post Crash Seatbelt Use Investigation
Part of the investigation of any serious motor vehicle collision is an examination of the seatbelts to determine if the person in that seating position was restrained or not. The outcome could determine whether a ticket for failing to wear the restraint was issued or not but I suspect that more commonly the information was used to determine liability. If you were not wearing your seatbelt your award for injury could be reduced by the courts.