The 5th Amendment to the U.S. Constitution gives every criminal defendant the right to remain silent. This means that a criminal defendant has no obligation to testify or to call witnesses. When a defendant remains silent, judges instruct jurors that the defendant has exercised a constitutional right and that they cannot infer guilt from the defendant's silence. (To read the 5th Amendment, and other Amendments in the Bill of Rights, check out Nolo's list of The Most Important Cases, Speeches, Laws, and Documents, in American History.)
But there are some excellent reasons why even innocent defendants might remain silent at trial:
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?