The solution is: You're not gathering evidence. Instead, you are making sure that deliverables are clearly defined, and expectations are clearly understood. T

The solution is: You're not gathering evidence. Instead, you are making sure that deliverables are clearly defined, and expectations are clearly understood. Then it becomes binary: did they meet expectations, or did that fall short. Your evidence is properly documenting that you clearly communicated deliverables and expectations, AND the other person understood and agreed to both.