FBI would need to prove a lie anyway. Not the easiest thing.
Edit: Some of these responses seem to be assuming "Don't lie" is the logical complement of "tell the truth". That is not the case.
Anyway, "tell the truth" is not a real strategy. That is: the sentence is essentially meaningless. We already know that actual truth is impossible to capture.
FBI would need to prove a lie anyway. Not the easiest thing.
Edit: Some of these responses seem to be assuming "Don't lie" is the logical complement of "tell the truth". That is not the case.
Anyway, "tell the truth" is not a real strategy. That is: the sentence is essentially meaningless. We already know that actual truth is impossible to capture.