On the stand, Greenberg explained how he quickly refunded money to a buyer once who claimed he had sold fake wine.
"I stood behind my wine as I always do and gave them a refund," Greenberg said. "I have nothing to hide."
Greenberg maintains through his lawyers that the ultimate test is to taste the wine itself, a luxury that also can devalue bottles that can cost thousands of dollars.
"The only way to know ... is to taste what's inside the bottle," Shartsis said.
Shartsis was not permitted to tell jurors that Koch is a billionaire, but he dropped some hints.
He noted that Koch spent $3.7 million buying 2,600 bottles of wine from Greenberg and paid a man more than $75,000 daily for two days to make his bids for him at the auction. He criticized Koch for failing to hire people to inspect the bottles he intended to purchase before the auction.
The dangers of trading in rare wines was already apparent to Koch, who learned in 2005 that four bottles of French wine he believed had been once owned by Thomas Jefferson were fake.
Since then, he's been on a bit of a crusade against wine fakery, having sued wine companies, auction houses and Greenberg, saying in court papers that counterfeiters for years "have duped wine collectors into paying millions of dollars for near worthless bottles of wine."