William Koch began testifying Wednesday in the civil case he brought against one-time billionaire Eric Greenberg, a California businessman who sold him wine in 2005.
Koch claims Greenberg cheated him out of more than $320,000 by selling him two dozen fake bottles of wine. Greenberg has testified he never intentionally sold a fake bottle of wine.
Koch says he buys very few bottles at auction anymore because he's "tired of buying fake wine."
Koch is the brother of famous industrialists and conservative political supporters David and Charles Koch.