What if Miranda rights aren't read?

Question

So I know that it's not quite like you see in TV and movies where a dead-to-rights murderer or rapist will just walk free because the arresting officer forgot to read their rights during the arrest. What, if anything though, could result from a person not being informed of their rights? Also, I'm proposing a scenario where someone is arrested on very serious allegations but divulges possibly incriminating information and does not ask for a lawyer, so they probably don't understand their rights.

Answer 1

If a person is arrested and not apprised of their rights, anything that they say cannot be used in court, but perhaps conviction does not depend on the defendant's statements. Even without the warning, your statement can be used against you for purposes other than proving criminal guilt, for example the statement can be used to attack your credibility (Harris v. New York, 401 U.S. 222), also it can be used for sentencing (U.S. v. Nichols, 438 F.3d 437). Also, there is a "public safety exception" New York v. Quarles, 467 U.S. 649, in that example the defendant, un-warned, answered a question about where he put a gun in a store (thus posing a threat to public safety) – it was not deemed necessary to read him his rights first before asking where he put the gun. In addition, if the police learn a fact (e.g. about a witness or evidence) which the police can lawfully track down, the evidence / witness is admissible (the defendant's statement is not itself introduced as incriminating evidence).

More generally, anyone who doesn't say "I want a lawyer" when they are being interrogated probably does not understand the case law surrounding the 5th amendment and the concept of "adoptive admission". Here is a brief summary.