You wouldn't. The whole point of these friendly competitions is pure honor system. You expect everyone is making a legitimate go on the game, and why shouldn't you if you're participating? .
Anybody can use emulators, save states, or slow gameplay to play a perfect game of Ms. Pacman forever until they reach 500,000 points. But the whole point of doing these things is having fun and seeing how well you can do with a legit straight up play. You simply do not expect anyone to actually "cheat" because again, "why" would you even bother? To show off your fake high score in a friendly competition? That's some sad stuff man..
Sad yes, but sadly true in this case. We've pretty much come to the conclusion via some private PM conversations that he has, in fact, been seriously cheating sadly all the time probably. Honor system is easy for us playing on real hardware, we can't cheat. And yeah, it's just a game, but how about emu players take the time to put in a little effort and record their work? It's really not complicated. Or, perhaps, we do it like this:
Two scoring systems, or rather two columns or brackets. All scores submitted, and those that have been proven. This means scores submitting on real hardware or emu scores proven via video. All can "participate", but only the scores in the proven category count towards the real competition. So you could have two separate winners, in theory. That feeling of "I'm not really a winner" would give me personally the incentive to record and prove if I was using an emulator. Seems like a pretty simple idea and easy enough to implement. NIKON has already talked to me extensively in PM how he's able to record and cut raw video down to reasonable file and time size for display on here. It's simple.