When I was still in college, one of my colleague, who happened to be an Electronics Major gave me a trivia that it is current, not voltage, that really kills a human. A milliamp of current is more than enough to kill a man.

I found it hard to believe because as far as I know, mainly base from observation, the higher the voltage of the electric source, the higher the risk of getting electrocuted. That is, a 220 V is more likely to be deadly unlike a 5 V battery. So how could that be if its current that kills? Does it mean that it is actually safe to touch a higher voltage wire?

Actually, what he just said was true but misleading. True because current which is a physical quantity (current is basically the flow of electric charge from the electron per second) that can flow into the human’s body and burn it. Misleading because voltage, which is just a potential difference, is the one that causes the current to flow. With the exception of super conductivity, current cannot flow without voltage difference between two points of the conductor. The higher the voltage, the higher the amount of current that will flow into the human body. The higher the voltage, the higher the risk that you may die from electrocution. The idea is as simple as the Ohm’s Law.

Just to add more. Some says that it’s like a “chicken and egg” scenario. But it’s not! You cannot produce a flow of current along a conductor without voltage difference, where as, you CAN have a voltage difference even without a current flow.
More trivia:

Q: What Value of current can kill?

A:
1MA = Tingling feeling

5MA = Pain

6MA = Female let go

10MA = Paralysis/male let go

15MA = Hazardous

30MA = Breathing Stops

75MA = Ventricular Defibrillation

100MA = Dangerous to life

4.0 A = The Heart Stops

5.0 A = Death/ Skin burns

MA = milliamp
A = Amp