I always double and triple check everything including a final check
with a non contact voltage tester. I've seen so many wierd things
working on clients electrical setups. You know the "What in the
F=2E....." moment and its another one for the books.
This sounds like a pertinent case:
http://www.cdc.gov/niosh/face/stateface/wi/93wi214.html
"A 45-year-old male electrician (the victim) was electrocuted when he
contacted an energized =BD-inch metal-cased electric drill.... There were
puddles of water on the cement floor of the work site. The drill was
connected to a temporary power pole by a series of three extension
cords, two of which were missing the ground pin.... The cords were
plugged into a ground fault circuit interrupter (GFCI) receptacle
mounted on the power pole. ... However, testing after the incident
disclosed the GFCI was inoperative, and the fuse box for the 120 volt
single phase 15- and 20-ampere receptacle outlets located at the power
pole contained two 40-ampere fuses."

Richard