You realise you've got the story entirely back to front?
Paton was charged with a very serious assault. Which he pled not guilty to. The chief prosecution witness (after Zaluska himself failed to show) gave evidence that the complainer was steaming drunk, acting like a complete bell end and threatening Paton. Paton gave him a slap. Realising that their case had collapsed the prosecution were only too happy to drop the original charges in return for a guilty plea for a minor assault. Paton generously accepted their offer. Classic case of the PF grossly overcharging in the first place.