What can high voltage do to you?

Answer 1

The really dangerous thing is how many electrons per second travel in the human body and this is the current. So the current is the "dangerous" part, and, as i remember correctly,

if you stick(similar to electrolysis where your blood acts as an electrolyte ,here current is directly set up in the electrolyte) 2 electrode needles in your body, a 9V battery is sufficient to electrocute you (because the resistance of the electrolyte in the blood is really low and so the current is high), but if you don't stick(just touching the too needles with hand etc etc..) anything in your body but only touch two wires, the tissue resistance is high enough and the 9V battery is harmless.

Answer 2

Most fatalities from high-voltage shock are caused by the resulting severe burns.