[meyer]

Its not the voltage that kills ya, its the current. Car batteries have a hell of alot of "cranking" AMPS. Try hooking jumper cables to your battery then touching the other side together. You can feel the current and see the pretty sparks.

Current flow is a function of voltage and resistance, as per ohm's law. The human body's resistance, even under worst case conditions, is almost always high enough that you won't even feel a 12-volt battery. You can't get 400 amps to flow through a 10,000 ohm resistor with 12 volts.

You're talking about whole different scenario when you talk about shorting the battery. You're unleashing the battery's stored energy in a short-term burst. I have a melted wrench from just such a thing - tightening the positive cable end while touching the car's body produced a pretty big spark and put quite a nick on both the wrench and the radiator core support structure. Though it did startle me a bit, I would hardly qualify it as torture. This is why, on a negative ground system as found in nearly every car, you should disconnect the negative first and re-connect it last.

[myself6]

Voltage and current are inversly proportional, for example, as the voltage goes up the current goes down.

A 12 volt potential is not enough to cause a great current flow through a 10kohm resistor but clean human skin is not a 10Kohm resister, more like 500 ohm. Add water and the surface resistance goes down further.

I = 12V/500 = 0.024A > 0.01A = pain

Enough to cause pain and discomfort to sensitive areas but not death. But then again thats the point of torture isnt it.