Answer:
says he is sane, but then describes how cleverly he hid the body.
Step-by-step explanation:
You can evaluate the narrator's state of mind as unreliable when he "says he is sane, but then describes how cleverly he hid the body".
When the narrator said that he is sane but he describes how he cleverly hid the body, then we can conclude that his state of mind is unreliable. Therefore, evaluating the narrator's state of mind, we cannot trust him - we can't rely that he is sane.