Alphitomancy is a form of divination using a barley leaf.
It is used to identify a thief or criminal.
Pieces of the leaf were given to a group of suspects.
If you were innocent you would feel no effects, but if you were guilty you would become sick.
Divination
Exploring Scrying: How to Divine the Future and Make the Most of It (Exploring Series)
Paralumun New Age Village