In cases where it has been proven that an alcoholic beverage retailer knowingly sold alcoholic beverages to a person who was clearly intoxicated at the time of such sale or sold under circumstances where the retailer reasonably should have known the person was clearly intoxicated at the time of the sale, a civil jury may determine whether or not the sale constitutes a proximate cause of any subsequent injury to other persons. For purposes of this section, a person is considered clearly intoxicated when the person is so obviously intoxicated to the extent that, at the time of such sale, he or she presents a clear danger to others. It shall be an affirmative defense to civil liability under this section that an alcoholic beverage retailer had a reasonable belief that the person was not clearly intoxicated at the time of such sale or that the person would not be operating a motor vehicle while in the impaired state.