Originally Posted by Pete P
I think 12v is enough to really injure, if it has enough current.
9v to open skin (Like poking your thumbs with multimeter probes, enough to pierce the skin) can kill.
Fleas possibly. Not humans.
Electricity kills one of two ways. Burning and interfering with muscles.
12V DC isn't enough to interfere with muscles, and even sticking your tongue across a 12v battery pack terminals gives you no more than a nasty sort of taste. Certainly no blisters.
You need around 40-50V AC to start to be dangerous.