Automated External defibrillator?
Yes, they're real life savers during shock incidents, and very simple to use.
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A GFCI in series with your rig might prevent even a suicidal test subject from being successful.
Not if it's inserted in the power cord feeding the guitar amp. Since I'm biasing the safety ground using a B&K variable AC supply, the GFCI would never see an electrocution fault current to an external ground. However, if I added a GFCI into the incoming AC powering the entire test rig, then that should protect a suicidal test subject from an external ground fault shock.
Unfortunately for me, my test bench has a few line-to-neutral shock points that a main power GFCI wouldn't protect me from. That's because a GFCI won't trigger on a line-to-neutral current, only line-to-ground faults. But I'll think of how I can improve the safety of my demonstration since 120-volts can easily be lethal. It LOOKS dangerous because it IS dangerous. So kids, don't try this at home...