Do the police have to read the Miranda warnings when I'm arrested?
No. This is a common misconception, because on police shows on television, when a suspect is placed under arrest, the police read him the Miranda warnings. The truth is, though, that the police do not have to read the Miranda warnings when you are arrested. Miranda applies to custodial interrogations -- and frequently, the police won't read your Miranda warnings when they arrest you in the hopes that you might say something incriminating. If you make an incriminating statement and it's not in response to a question by a police officer, your statement can be used against you in court.
So then, what's a custodial interrogation?
It's any questioning by the police when you are in custody, i.e. under arrest. Now, what constitutes "in custody" can be hazy at times. If you have actually been placed under arrest and taken to jail, you're clearly in custody. But other situations can sometimes be confusing. The legal standard is whether a reasonable person would have believed that he was not free to leave. If you're in the interview room, you're not handcuffed, and the door to the interview room is left open, a judge reviewing the case is probably going to believe that you were free to leave. But what if you were escorted to the station in the back of a squad car? Maybe not. Or what if the police lock the door to the interview room and question you for eight hours, and don't tell you that you're free to leave at any time? That also is likely to sound to a judge like you were in custody.
So what happens if the police did violate my Miranda rights?
Another common misconception regarding the Miranda warnings, of course, is that you're entitled to have your case thrown out if the police didn't read the Miranda warnings. That's also not true. The only remedy available for a Miranda violation, in most cases, is to have your statements suppressed -- meaning that they can't be used against you at trial. But the police and prosecutors may have other evidence to use against you even if your statements are suppressed.
Really, what's your advice about all of this?
The simplest advice, of course, is not to talk to the police. In most cases, once the police have reached the stage where they want to ask you questions about a crime that you're accused of, they've already decided that they're going to arrest you (even if they haven't actually gotten an arrest warrant yet.) At that point, they really just want you to confess to the crime or make incriminating statements that they can use against you at trial. Talking to the police usually won't help your cause, and will only hurt. It's generally a safer bet to simply refuse to answer any questions, which you have the right to do under the Fifth Amendment. And if you absolutely insist on talking to the police, which I don't recommend, then have a lawyer present when you do.