After even a minor mishap, most people seem to apologize or look embarrassed almost immediately, even if it's unnecessary. I'd bet that the presence of this response is good evidence that the person is not a sociopath.
Like pain, embarrassment causes a clear physiological response, and one that should be hard to fake - - at least consistently.
Psychopaths can and often do imitate normal pro-social emotions, but to do so quickly and consistently, even in the most minor circumstances, should be hard. The opposite, to quickly and consistently suppress a response should be easier (and monks seem to be able to do this, at least for negative reactions).
So whenever I see someone blurt out a sheepish "oops!" when opening a door into me at work, I mentally check him or her off the "possible psychopath" list. Everyone else is still on it ;)