"The first practical electric chair was invented by Harold P Brown who worked for Thomas Edison."
Hmph. Well, possibly, for a given value of "practical". The electric chair was touted by Edison who wanted to demonstrate how dangerous Westinghouse's AC system (the competitor to Edison's low-voltage DC proposition) was by comparison. Edison tried very hard to get "electrocution" into the public consciousness as the verb "to westinghouse" but it didn't stick.
By all accounts, it wasn't terribly practical at all. William Kemmler, the convicted murderer who entered history as the first man to be deliberately executed in this way, was zapped for a good 17 seconds on the first attempt which noticeably failed to kill him. They left him strapped to the chair, uttering presumably quite vociferous complaints as to his mistreatment, for some considerable time until they could charge the generator up sufficiently to give him another blast... They cranked up the voltage and this time gave him a full minute, which did the trick but in a spectacularly gruesome fashion.
Westinghouse later commented that the execution would have been better performed with an axe. Even allowing for a certain disgruntlement on his part at the tackiest PR episode in history being aimed at his AC current system, that doesn't really sound like a "practical" electric chair to me!