Somewhere in the 1500-2400V range seems to be the norm, but apparently the systems used (or formerly used) in some states would automatically cut the voltage back after a few seconds.
I've found documents which state that the Georgia chair, for example, was specified as 2000V for 4 seconds, followed by 1000V for 2 seconds, followed by 208V for the remainder of the 2 minute cycle.
I've seen another spec (VA I think) which applied something like 1800V for 15 or 20 seconds, followed by 600V for another 40-45 seconds.
The explanation is that the initial higher voltage is to knock out the brain and render the prisoner unconscious as quickly as possible, then the reduced voltage is to minimize burning. The 1 to 2 minute cycle is supposedly necessary to ensure complete cardiac and respiratory failure.
All texts that I've read suggest that most of the resistance of the human body is in the outer layers of skin. Once they are broken, the resistance of the body tissues inside is quite low. Another point I've seen put forward for the high voltage is that it breaks down the skin's insulation and allows a greater current to flow.
I recalled a discussion we had about this some months ago, and I found the link from back then. The table below gives voltage and current readings from Florida's chair, which in its modern form apparently had a more sophisticated control system which regulated the current by reducing the voltage as necessary during each of 3 cycles.
The last five executions provided the following:
Inmate Cycle Volts Amps Ohms
Buenoano
1 2000 9.4 212.8
2 650 2.9 224.1
3 1900 9.4 202.1
Remeta
1 2100 9.2 228.3
2 675 2.9 232.8
3 1850 8.9 207.9
Stano
1 1600 9.1 175.8
2 550 2.9 189.7
3 1500 9.0 166.7
Jones
1 1600 9.1 175.8
2 500 2.9 172.4
3 1450 9.2 157.6
Davis
1 1500 10 150
2 600 4.5 133
3 1500 10 150
Just see how low the resistance of the body (head-to-ankle) can get.
{Edit: The auto formatting in the forum software has distorted the tables a little. They're from
this link .}
By the way, the case of Willie Francis referred to in the FAQ linked above is fairly well documented. Although he did indeed survive the first attempt at his execution, he did so only because the officials in charge made a mistake. Apparently Louisiana at that time (1940s) used a portable chair which was taken to the parish in question for each execution. A guard made the wrong connections which resulted in only 200V or so being applied when the switch was thrown (I'm guessing 208V from a normal 120/208 system?).
[This message has been edited by pauluk (edited 03-10-2003).]