Of course no one knows what happens to the electrical energy in a human upon death… but, it definitely leaves the body.
Of course we know.
Cells create electric potential by pumping different kind of ions in or out of the cell. That requires ATP which is produced during metabolism. If you’re dead your cells stop producing ATP and everything, including the ion pumps, stop working. So no more electricity.
It doesn’t “leave” the body. The body stops generating it.