"Electric Chair" joke

A chemist, a biologist and an electrical engineer were on death row waiting
to go in the electric chair. The chemist was brought forward first.
"Do you have anything you want to say?" asked the executioner,
strapping him in.
"No," replied the chemist. The executioner flicked the switch and
nothing happened.
Under this particular State's law, if an execution attempt fails, the
prisoner is to be released, so the chemist was released.
Then the biologist was brought forward.
"Do you have anything you want to say?"
"No, just get on with it."
The executioner flicked the switch, and again nothing happened, so the
biologist was released.
Then the electrical engineer was brought forward.
"Do you have anything you want to say?" asked the executioner.
"Yes," replied the engineer. "If you swap the red and the blue wires over,
you might make this thing work."