What was suspicion is now certainty. But what can you say or do?
Over time, the experienced golfer developes, through practice at the mirror, a range of expressions. Capable of conveying varying mixtures of doubt and disapproval, from mildish skepticism to the unspoken outrage felt on coming home to find that the family has been put to the sword by Mongol hordes.
Golfing with Cheaters? What do you do?
Without having been forced to say so in plain words, you want the cheater in your midst to head for the next tee thinking, "He knows. He knows!" I think you'll find that his ensuing play will more than compensate for any advantage gained through earlier defalcations.
Appropriately enough, in Scotland, the land which gave us the immortal pastime, there is a verdict that is handed down in trials where the evidence falls just short. It is called "Not Proven." What it means is: "Not Guilty-But Don't Do It Again." What you want to have in your psychological kit bag is the physiognomic equivalent of that verdict.