An object - an "exhibit" - presented as evidence is always overdetermined, despite the parties' attempt to narrativize it. It is the focus of a narrative that points to another narrative. Stonehenge. It's just there. But even a text is an object. That text is going its own way. It doesn't necessarily want to be part of your party.

All of which applies to any evidence. But in art, unlike law or science, rules of evidence are less codified. The gap between the thing and the narrative it is supposed to represent can open a creative (imaginative) space.