But I would claim, and I think this is a reasonable assumption, that electric fence chargers are "not designed to cause, or known by the actor to create a substantial risk of causing, death or serious bodily injury".(1) the device is not designed to cause, or known by the actor to create a substantial risk of causing, death or serious bodily injury
They are apparatus that the manufacturer knows will come into contact with people, usually by accident of course, and so they're designed to inflict some pain but not permanent damage nor death.
If my flag had twice been stolen,
I'd put one on it in a heartbeat and wait for the screaming. 
