Note that it's not possible for an honest person to have need of the 5th amendment.
That really isn't true...
incriminate: make (someone) appear guilty of a crime or wrongdoing; strongly imply the guilt of (someone).
Note the word "appear". There was a robbery down on Main Street last night. Where were you last night? If you were to answer that you were on Main Street, you could well be incriminating yourself, even if you were to know nothing about the robbery.