I always turn the breaker off when I do any electrical work, earlier this afternoon my father in law when to my wife's work to install a new light fixture basically all he did is turn the light switch off and started the wiring well we can all figure what happened next. He came home with a black thumb and was saying sparks were flying not much surprised there. Now I was thinking since the switch was OFF how is it possible to get electrocuted? Is it that the wires are still energized? Basically the HOT wire is broken by the switch when the switch is in the OFF position so how is it possible that current can still flow into the rest of the circuit?