But G.G. Gallup's mirror experiments, from the mid-1970s, are a particular favourite of those prowling for overt evidence.

Sacagawea merely sat impassively, showing no overt evidence of having even understood the question.

"We found no overt evidence that any fix existed."

He said there was "no overt evidence" that the officers' actions were racially motivated, although he said his prosecutors tried to imply that to the jury.

"Nor I, although there is little overt evidence."

There were no laundry marks or overt evidence connecting them immediately to Brandon Scofield; fingerprints would do that, but lifting and processing them would take time.

Lord Kian saw that all overt" evidence of the battle was gone.

Grosvenor did not expect overt evidence, and so he was not disappointed.

He was said to have "extreme Sensitivity to criticism and strong desire to receive overt evidence of public support".

He would be aware that others might view the message, and would not be so foolish as to provide overt evidence of threats for all to see.