How do I prove a motel room was undamaged before the guest checked in?

Every room damage claim contains a hidden second claim, which is a claim about the past. You are asserting not only that the room is damaged now, but that it was not damaged before this guest arrived, and the guest's easiest defence is to attack the second half. A condition record at check-in answers it outright, and it does not need to be elaborate. A dated photo set taken at turnover, stored automatically, converts the strongest available defence into nothing. Properties that adopt this find it changes outcomes more than any argument they could make later.

Without one, you rebuild the same fact from people and process. The housekeeper who cleaned and released the room can testify that it was clean and undamaged when they finished, and a signed turnover checklist showing the room was released to sale carries similar weight. Prior guests are relevant too: if the room sold the night before with no complaint, that is meaningful, because occupants do complain about damaged rooms. Weakest of all is the owner asserting from memory that the room was fine. It is not that a judge disbelieves you, it is that the guest's contrary assertion is exactly as good.