Exclusionary Rule

The exclusionary rule permits a criminal defendant to prevent the prosecution from introducing at trial otherwise admissible evidence that was obtained in violation of the Constitution. In a sense the term "exclusionary rule" is misleading, because there are many exclusionary rules. Some, such as the rule against hearsay, exclude evidence because it is not very reliable. Others, such as a rule prohibiting a witness from testifying if the calling party did not disclose the witness before trial, are sanctions for the failure to comply with a nonconstitutional rule.

While every legal system excludes some evidence deemed irrelevant or untrustworthy, the constitutional exclusionary rule is unusual in rejecting highly probative evidence, often with the consequence of nullifying a meritorious prosecution. It is therefore not surprising that the exclusionary rule has occasioned sustained and sometimes bitter controversy.

A simple example helps to explain both the practical operation, and the controversial nature, of the exclusionary rule. Suppose the police stop a driver for speeding, and in the course of issuing the citation they discover cocaine in the glove compartment of the car. If the defendant did not consent to the search, and if the police did not have probable cause to believe illegal drugs could be found in the glove compartment, the search would be illegal under the Fourth Amendment.

To invoke the exclusionary rule the defendant would move before trial to suppress the drugs as illegally seized. This motion would be decided by a judge sitting without a jury. The defense would have the burden of proving that the defendant's rights were violated. If the facts are disputed (as they usually are), the parties would be allowed to call witnesses. If the accused testifies at the suppression hearing, this testimony is not admissible against him at a later trial.

If the judge decides that the search was illegal, the exclusionary rule comes into play and the evidence will be suppressed in the pending case. In our example, the government has no case without the drugs, and the court would have to dismiss the charge. Note that the defendant who moves to suppress incriminating evidence is usually in fact guilty. Maybe the driver had no idea that someone else had put cocaine in the glove box, or maybe the officer planted it, but the most likely hypothesis is that when there is physical evidence to be suppressed the person seeking suppression is indeed guilty as charged.

Note also that the rule does not automatically result in acquittal. Suppose the police found cocaine in both the glove compartment and the trunk, and the court ruled that the cocaine in the trunk was seized illegally but that the search of the glove compartment was legal. The suppression of the cocaine from the trunk would not protect the defendant from being convicted for possessing the cocaine in the glove compartment.

Note, finally, that the rule does not require returning contraband to the defendant. If the evidence at issue were lawful to possess, such as a diary or a properly registered firearm, the defendant would be entitled to its return at the close of the proceedings. Even when contraband is illegally seized, however, the defendant is entitled only to its exclusion from evidence, not to its return. Were it otherwise the defendant could be arrested on the courthouse steps for possessing the returned contraband.

If the judge grants the motion to suppress, the government would be allowed to appeal before a verdict is entered on the pending charge. Otherwise, the double jeopardy clause would bar appellate review of the trial court's decision to grant the suppression motion. If the judge decides that the evidence was not seized illegally, the motion will be denied and the case will be set for trial. If the defendant is convicted, he will be free to appeal on the ground that the trial court should have granted the motion to suppress.

Why does the law permit the guilty to escape justice because the police violated the Constitution? Would it not make more sense to admit the evidence and punish the police by demotion or suspension, or through civil lawsuits? The standard explanation is that these alternative remedies for constitutional violations have been found, in practice, to be ineffectual. Law enforcement agencies have not shown the willingness to discipline officers whose excesses lead to successful prosecutions. In civil suits against the police, the damages juries might return for illegal searches, together with the good-faith immunity defense available to the police, have blunted the deterrent force of the tort remedy. Freeing the guilty is not very appealing, but doing nothing about violations of the Constitution has seemed even worse.