Comment by GuB-42

Detecting flesh using electricity probably dates back from the voltaic pile, more than 200 years ago.

But it wasn't used to stop sawblades. How to reliably detect flesh without too many false triggers, do it fast enough, on a spinning blade, and as part of a complete system that includes the brake and actuation mechanism. That's what the patent is about, not the vague idea of using electricity to detect flesh.