Legal Question in Criminal Law in Washington

It depends. The basic Miranda rule is that if a suspect is "in custody", the interrogator must advise of Miranda rights prior to any questioning designed to elicit an incriminating response.

So, as you can imagine, there are many loopholes. If the suspect wasn't in custody, just being detained briefly, then no Miranda required. If the interview was by phone, no Miranda needed. If the suspect just offered information, without being specifically asked, no Miranda needed.

And ultimately, even if there was a Miranda violation, and even if you could prove it, the case can still go forward. The only penalty to the government is that those answers given without proper warnings can't be used in court. Commonly, there is enough evidence to prove the case even without those answers.