Well, accident or not, there's no way to tell either way - like drawing an extra card (you know, like grabbing two instead of one). I understandwhere you are coming from, but especially lately, you HAVE to call the judge for every little thing.
Let me give you an example.
This one guy that I've played, and lost two twice, is playing me in a booster draft. A friend comes up to me and tells me about how much of a cheater he is. The reason he wasn't caught supposedly was because the cheating was going on druing a FNM, and the WotC staff there just told him to stop what he was doing.
To quote him about it during my match with him: "Stalling isn't cheating, is it?"
So anyway, I'm like you. I only call over the judge for blatant rules violations and rules questions. We go to shuffle, and I notice that he's riffle shuffling upside down, followed by slight, deliberate riffle shuffles. I think nothing of it because I'm going to shuffle his deck quite a bit anyway (probably 10 riffles would do it).
I win the first one, and we start the second one, and I notice that his shuffling is getting more deliberate. I again make nothing of it because I'll just shuffle his deck. I lose badly, and same thing happens in the third game. Looking back on it, my deck was far superior to his, and there must have been something going on (deliberate shuffling, one instance where he tried to regenerate a Nightscape Familiar with two Islands, ect).
So I go over to the local lvl 3 judge, and I ask him what I should hve done. And he told me bluntly that I should have called a judge immediately when he presented his deck. And when he payed incorrect costs for things.
You also have to remember that some people enjoy playing seriously. Some of us may not like to win a game with an Ancient Silverback or build Glowing Anenome.dec.
