Some Ideas to show proof!

well, what realm u in? if so in the same realm as some1 esle on this site(or fourm), then have them give u a item, thendo the method, wait for it to dupe,(if it takes like a week then forget it) then show him the item, but the item(s) ur gonna let him dupe shouldn't be ones he already has or something... use something like Kalhim's Awe