king's evidence

Probert, who had been mixed up in the affair, was admitted as Kings evidence and discharged at the rising of the Court.

Hare, a young man then, turned kings evidence and received a pardon.

If you are not, you will probably be admitted kings evidence; though, mind, I make no promises.

This, of course, was scarcely correct; but the Observer put it right by stating that Hare had agreed to turn Kings evidence.

On this he turned kings evidence, and his accomplices were convicted.