You've already received two rational and plausible answers, and all I'm going to do is reinforce that. We are capable of doing some pretty strange things while asleep. I was visiting my parent's one time, and I woke up in the morning to find a completely full glass of milk balanced on my chest. It's amazing I didn't spill any, my hands were cupped around the bottom of it, and there it was, right on my sternum, just like it belonged there. The bedroom door was closed, the blankets were pulled up around me, nothing in the kitchen was disturbed or out of place; nevertheless, there was that glass of milk filled to the brim.
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That's a pretty complex series of things to do. Get out of bed, open the door, get a glass from the shelf and close the cupboard, open the refrigerator, pour the milk and put it back, return to the bedroom, close the door, get back into bed, pull the covers up, pick up the milk and lay back down with the glass balanced on me. Not believing in the supernatural, the only alternative I can think of is that one of my parents put it there before I woke up, but how implausible is that? Neither one of them have been much in the way of practical jokes, other than the old fly-in-the-plastic-ice-cube trick, and who would try this even if they were jokers? All you're likely to end up with is a bed full of milk and a really pissed off house guest. So, it had to be sleepwalking, as bizare as it seems. It's a pretty baffling thing to wake up to, I can tell you that, and I'm still amazed I didn't spill it. The glass was full right up to the brim, too--there was no room for error.
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I told this story to a kid at work, and he replied with one of his own. He had woken up with dirt on his hands, and was baffled because he knew he went to bed clean. A few nights later his wife caught him sleepwalking, he went out into the front yard and was digging a hole in the flowerbed with his hands, apparently dreamed he had something to plant and so he got right to it.
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I remember someone trying to use a sleepwalking defense in a murder trial maybe a decade or more ago. People at work were really rolling their eyes on that one, and I'll admit I was too, I can't imagine how one could not wake up with someone screaming at him. I'm certainly not as positive about it as others were, though, not after my experience. While it's sure not bloody murder, I would have assigned about the same probability to either story, except that I happen to be positive that mine really happened. The sleeping mind can do some very strange things, and given my experience, I find it well within the realm of the possible that you could have done this yourself. I'd apply a double digit probability to the son being involved, and about a thousandth of one percent of anything supernatural. Anytime there's an even remotely plausible explanation, Occam's Razor demands that we discard the supernatural choice.
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