The key point here is that the police can lie to you. They can tell you they have evidence that you did it, they can tell you that your buddy is blaming you, th

The key point here is that the police can lie to you. They can tell you they have evidence that you did it, they can tell you that your buddy is blaming you, they can answer your phone while they're in your house and pretend they're you, and so on. The police are not obligated under any kind of ethical rule to tell you the truth. Deception is fine. Of course, if you like to a federal agent, it's a felony. That includes everybody from tax collectors to folks from the Farm Bureau. If you lie to state or local policemen, they can use that against you as evidence that you were trying to be evasive. This is true even if you accidentally omit something or just get confused. It's all free ammo for them to use. This is why the only thing to do when questioned by the police is shut up and ask for a lawyer. Even if you are innocent and have nothing to hide[1] [1] Admittedly this is very difficult to do in situations where you are completely innocent and a life is on the line, for example if the cops are looking for a missing person. Personally I try to help all I can. But from what I understand you are gambling here that the police will intuitively grok you as a "good guy". If their perceptions change, even in error, informally cooperating is a fool's game and you could get screwed royally.