Exactly put Scot. You can't tell what severity of shock has been received by a victim, because you won't know the atual resistance value. Some values in milliamps-
1ma- just about felt.
5-10ma- If victim is grasping the conductor -he can't let go!
20-50ma- possible fatality due to fibrilation of heart system and temporary paralysis of respiration.
60-800ma- probability(!) of death, burns.
Above that, muscle damage, internal and external burns, VERY life threatening. Or-

At 120v, dry skin 100kohm = 1.2ma=tingle
At 120v, wet skin 1000ohm = 120 ma=serious.

WHAT TO DO in an ELECTRIC SHOCK EVENT?-
* DONT TOUCH VICTIM until SURE he/she is disconnected from the source of the shock.
-seems obvious, but many victims are hapless 'rescuers'.
* Call 911 (999 UK) for urgent medical assistance.
* Apply first aid, possibly CPR (artificial respiration UK). You MUST know what you're doing- a wrong actio can make it worse, but prompt & proper action may save a life, because a common symptom is a temporary breathing stop. This isn't the place to discuss the finer details of CPR- Go on a First Aid course!!-Far better to say to a victim's family "Aw-it was nuthin!", than going out to buy a black tie....
Alan

Wood work but can't!