In order for the victim to prove if defamation occurred or not it really depends on the status of the victim. If the victim is a private figure the victim simply need prove that a false statement was made about the plaintiff to a third party that it was published and that the plaintiff was damaged or harmed. Usually because people didnt want to do business with the plaintiff anymore so usually the plaintiff would have to show some sort of economic damage so its a hard burden to prove. And thats why a lot of defamation cases get thrown out. Now the burden for the public figure is a more difficult burden because that plaintiff also needs to prove in addition to the statement being false that that statement was made with malice or conscious disregard for its truth and therefore the public figure has a much higher burden to prove. And the reason is because the public figure has voluntarily thrust him or herself into the public light