Only once, for your basic pub carpark scuffle. The presentation by the prosecution was that the defendant had started the fight, and when the other guy went down, he'd stamped on the other guy's leg to break it, and then kicked him in the head.
Trouble was that the prosecution solicitor was a waste of space. Facts that came out from all witnesses (mostly the injured guy's friends) and importantly a doctor were that:-
1) Yes, the defendant had shouted across the carpark, but the other guy then came over to him and took a swing at him.
2) The defendant was losing the fight until the other guy slipped and fell. The broken leg was a twisting fracture, and couldn't have been caused by stamping. And all the other guy's friends said that the defendant hadn't ever stamped on his leg.
3) No-one could show that the defendant would have known the other guy's leg was broken, or that he couldn't get up.
General opinion on the jury was that the defendant was a nasty little toe-rag. But also that had anyone from the CPS done their jobs properly and looked at the defence case, it should never have gone as far as a jury trial. Opinion was divided on whether he was justified in putting the boot in, and that made it a mistrial because the required majority (10:2) wasn't happening. I never saw anything in the papers afterwards, so I guess the CPS dropped it.
As the main person speaking up in favour of him putting the boot in (because I know damn well I'd have done it myself if some big bloke was beating up on me and then happened to fall over), I'm glad I was present. Still, it did show that the standard of CPS solicitors is pretty damn poor.