If a police officer questions a suspect who is in custody without giving the suspect the Miranda warnings, nothing the suspect says can be used against the suspect at trial. The purpose of this "exclusionary rule" is to deter the police from violating the Miranda rule, which the U.S. Supreme Court has said is required by the Constitution. (Dickerson v. U.S., U.S. Sup. Ct. 2000.)
(For more information on evidence that might be inadmissible after a Miranda violation, see our article on "fruit of the poisonus tree.")
In the years since the Miranda case was decided, several exceptions to the above rule have emerged from the courts. The exceptions assume that the only reason the statement is inadmissible is the Miranda violation and not other possible forms of police misconduct, such as physical coercion.
VARIATIONS ON A THEME
Though many critical rights come from the U.S. Constitution, states have their own constitutions and statutes. State law often provides protections that are similar, if not identical, to the those the federal Constitution gives. But occasionally state law offers expanded rights. Keep this potential expansion in mind when reading about general criminal law principles. It could be, for example, that evidence that would be admissible under the federal Constitution is inadmissible under state law.
For more on applicable law and your rights, see this note from our editors.
If a defendant gives testimony at trial that conflicts with a statement made to the police, the prosecutor can offer a statement elicited in violation of Miranda to impeach (attack) the defendant's credibility. (Kansas v. Ventris, U.S. Sup. Ct. 2009.) Similarly, rules in many jurisdictions allow prosecutors to offer statements obtained in violation of Miranda against defendants in sentencing hearings. (U.S. v. Nichols, 4th Cir., 2006.) For example, assume that in an improperly obtained statement, a defendant admits to the police that he was armed with a weapon when he committed a crime. The defendant's confession may not be admissible at trial to prove the defendant's guilt, but the prosecutor may offer it into evidence during sentencing to try to obtain a harsher sentence.
Here are some other common exceptions to the Miranda rule:
These exceptions arguably give the police real incentive to violate the Miranda rule. Suspects sometimes mistakenly think that what they say—or evidence found because of what they say—won't be admissible.