"Do you think it would be possible to glance over the persons shoulder (as if someone was there) to distract them to give you a few seconds to draw?"
IF you're that good of an actor.
IF the perp turns far enough for long enough (how fast can you draw and shoot?)
IF you manage to draw, cock, and shoot cleanly. Nothing gets hung up on your clothing or you miss hitting the safety, etc.
Lots of "IFs" there and you only got one chance.
Yea, we've all seen the stories that say it's possible to draw and shoot before the other guy can react. I'd hate to stake my life on proving it.