[z3n]

"I know PS enough to see faked areas even without a real one for comparison"

O rly? I can make modifications in photoshop that you will not be able to detect.
It's when people attempt to falsify entire documents that the errors are easier to spot, because you can find contextual, document, and formatting errors (Dan Rather). But if you want partial modifications of a valid document, you can reference the valid document for properties and patterns.

[TribalPrincess2U]

That’s pretty much what I said.