Answer:
Voltage does not kill, amperage kills. Voltage is a measure of potential energy, while amperage is a measure of moving electrons.
In general, the more voltage that is present, the more amperage there will be. But this is not always the case. A stun gun has a high voltage but little available amperage.
So, the correct question is "How much amperage can kill a man?". The answer varies, but should be around .1A to stop a heart.