Section - Evidence
A thing can be evidential. A thing is usually not evidential.
To decide if the player has evidence of (clue - a thing):
if the player encloses the clue:
decide yes;
if a photo shows the clue:
decide yes;
decide no.
To decide if the player does not have evidence of (clue - a thing):
if the player has evidence of the clue:
decide no;
decide yes.