The police officer who responds to the scene will likely be able to tell whether you were wearing a seatbelt and will note it in their accident report. In addition, they will speak with drivers and passengers from every vehicle involved and any witnesses. Your injuries may also provide evidence that you did not have a seat belt on, and if necessary, the other party may use traffic light cameras or dashboard cameras as proof.
Missouri Seatbelt Law
By law, all drivers and passengers in Missouri must wear a seatbelt at all times while a vehicle is being operated. When a passenger is under the age of 16, the driver is responsible for ensuring they have a seatbelt on. Failing to properly use a seat belt can lead to a fine and court costs.