Longman Dictionary of Contemporary English
Wikipedia
A prison visitor is a person who visits prisons to befriend and monitor the welfare of prisoners in general, as distinct from a person who visits a specific prisoner to whom they have a connection. Many prisons have a visiting committee.
Usage examples of "prison visitor".
Brother Robbins was speaking with the elaborate courtesy of a prison visitor: he managed to imply that beer drinking was a particularly squalid vice which he was too broad minded to condemn.
On his own, a double cross, I don't know, Davey sends Dean Van Gelder, his prison visitor, to talk to Cathcart.
A soft, dreaming, kindly idealist who would naturally leave the Service and become instead a prison visitor, interest himself in youth clubs, march with the H-bomb marchers, eat nut cutlets, try and change the world for the better?