So the last time we talked I told you to keep silent, but what if you talked? What if you told the nice detective that you bought the drugs from your source in El Paso, who just happens to take delivery across the Rio Grande from "Phillipe" and his brother. Well my friend – you’ve got trouble. Trouble. With a capital T and that rhymes with G and that stands for GUILTY! Usually. Suppose however that the cops went "Slumdog Millionaire" on you before you confessed, having hooked you up to a 12-volt and leaving you all shaking and unconscious. What then?
The first rule in confessions is they must be freely and voluntarily given. That’s what the constitutions (state and federal) require. Now I have never seen the car battery trick except in the movies, but I have seen plenty of bruises and heard plenty of stories about coercion. Not all are true, and if the officer promises to help you and take your story to the prosecutor, that is not coercion. Usually we are talking beatings, sleep deprivation, yelling and screaming, perhaps the "rubber hose," before a statement is coercive enough to get it bounced here. Promises and inducements may do it, but not usually. And the cops can lie to you to get you to confess – no problem there. Despite what you may hear, not many statements are thrown out for this reason.
The second rule is that a confession may be excluded from evidence at trial if you were not read your Miranda rights BEFORE you told them you stole the car or sold the drugs – BUT ONLY if you are in custody and subject to interrogation. Custody is usually pretty easy – if you cannot leave, whether they have "arrested" you or not, you are in custody. Favorite custodial settings include the police station, investigation room, police car or down on your knees with an officer over your head yelling that you may not move. Now, what is interrogation? Questioning intended to elicit an incriminating response. Like – "Leroy, where did you get all that heroin?" Seriously.
This short explanation is not intended to cover all the possibilities, as there are EXCEPTIONS to the rules that exclude some statements.
So what do you do when you have answered the questions? Get a good lawyer. He or she can review what happened, give you advice, file motions to suppress and maybe keep the statements out of evidence. Not every confession gets into evidence, but it is so much easier for the lawyer if you simply do not talk.