Damages are another issue that can come up during a defamation law suit. Can the plaintiff prove that the defendant's false statements caused actual monetary or emotional damage? A judge may award punitive damages if the slander was egregious, but the plaintiff may have to demonstrate real losses, too.
If an angry customer told people the owner of a restaurant spits in everyone's food, then the owner could sue for defamation. He would have to prove that a subsequent loss of business was due directly to the slanderous actions of that customer. People may have heard the accusations and chose not to believe them. However, if another customer testified that the defendant's accusations caused him to stop patronizing the restaurant, then there would be actual damages.