I didn't write this topic to scare anyone but to make you aware that in theory a 12vDC car battery can kill you, it isn't the voltage that kills you but the current passing from one arm through to the other arm. and it does not take a huge amount of current to cause your heart to fibrillate this means your heart does not stop but becomes erratic also know as a heart attack.
Fibrillation (which is what kills you) is perfectly possible with a 12VDC
battery in the 'right' conditions.
What it takes is 100mA through the heart (an acquaintance of mine got
killed this way doing a charging check on the 28VDC system in a
helicopter many years ago)
As your effective skin resistance varies, it will depend on your
effective resistance being about 80-100 ohms, and the current going
from one set of fingers to the other (so the current path is through
the heart area).
A word of warning don't assume its only 12v and it wont hurt me the acquaintance of mine was a healthy 21 year old.
If I check a battery now I keep one hand behind me, I don't touch the body work of my car at the same time I touch the battery terminals, if the battery is off the vehicle I don't touch both terminals at the same time.