No. However, if they start questioning you but haven't read you your rights, they can't use anything you say as direct evidence against you at trial. What are these rights? Popularly known as the Miranda warning (ordered by the U.S. Supreme Court in Miranda v. Arizona), your rights consist of the familiar litany invoked by TV police immediately upon arresting a suspect:
It doesn't matter whether an interrogation occurs in a jail or at the scene of a crime, on a busy downtown street, or in the middle of an open field: If you are in custody (deprived of your freedom of action in any significant way), the police must give a Miranda warning if they want to question you and use your answers as direct evidence at trial. If you are not in police custody, however, no Miranda warning is required. This exception most often comes up when the police stop someone on the street for questioning about a recent crime and the person blurts out a confession before the police have an opportunity to deliver the warning. (To learn more about Miranda Rights, read Nolo's article Police Questioning: When Miranda Warnings Are Required.)
Proof & Defenses in Criminal Cases
Getting a Lawyer for your Criminal Case
Steps in a Criminal Defense Case
Arraignment: Your First Court Appearance
Plea Bargains (Deals) in a Criminal Case
Legal Elements of Common Crimes
Expungement & Criminal Records
Should I just plead guilty and avoid a trial?
Is the public defender a real lawyer?
Can I change defense lawyers after I've hired one?
How long after arrest do I find out what the charges are?
Does it matter whether a suspect is given the Miranda warning?