Death Row.

A chemist, a biologist, and an electrical engineer were on death row waiting for 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 state law, if an execution attempt fails, the prisoner has 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."