usually they will ask the owner for the receipt, so if you have the receipt, and base on the purchase date is still within warranty period when the camera send in for repair, they will honour the warranty.
and camera store will write down the serial number of camera on the receipt.
if owner not able to provide receipt, they will take it as warranty period is over, service charge will apply. unless the model of this camera is extremely new, like release to the market for less than a year (provided it is a local set).