Exclusionary Rule
The exclusionary rule prohibits the use of evidence obtained through unconstitutional searches and seizures, serving as a deterrent against Fourth Amendment violations by law enforcement.
The exclusionary rule is a judicially created remedy that prohibits the prosecution from introducing evidence obtained in violation of the defendant's Fourth Amendment rights against unreasonable searches and seizures. The rule was applied to federal prosecutions in Weeks v. United States (1914) and extended to state prosecutions through Mapp v. Ohio (1961). Its primary purpose is to deter law enforcement from conducting unconstitutional searches by removing the incentive to obtain evidence illegally.
The rule applies to evidence directly obtained through the constitutional violation (primary evidence) and to evidence derived from the illegally obtained information (derivative evidence, under the fruit of the poisonous tree doctrine from Wong Sun v. United States). If police conduct an illegal search and find a map leading to additional evidence, both the map and the subsequently discovered evidence may be suppressed.
Several exceptions limit the exclusionary rule's scope. The independent source doctrine allows admission of evidence obtained through a source wholly independent of the illegal conduct. The inevitable discovery exception admits evidence that police would have inevitably discovered through lawful means. The attenuation doctrine admits evidence when the connection between the illegality and the evidence has become sufficiently attenuated by intervening circumstances. The good faith exception, established in United States v. Leon, admits evidence obtained by officers reasonably relying on a warrant later found to be defective, because excluding such evidence would not deter police who acted in reasonable good faith.
The exclusionary rule has been criticized as imposing too high a social cost — allowing guilty defendants to go free because of police error — and the Supreme Court has increasingly narrowed its application. In Hudson v. Michigan, the Court declined to apply the exclusionary rule to knock-and-announce violations. The current Court generally views the rule as a last resort applicable only when the deterrence benefits outweigh the costs of excluding reliable evidence.
Key Elements
- 1Evidence was obtained through a violation of the Fourth Amendment
- 2The rule excludes both primary evidence and derivative fruit of the poisonous tree
- 3Exceptions: independent source, inevitable discovery, attenuation, good faith
- 4The rule applies only when its deterrent effect outweighs the costs
- 5Standing: only the person whose rights were violated can invoke the rule
Why Law Students Need to Know This
The exclusionary rule is central to criminal procedure. Students must know the rule, its four major exceptions, and the ongoing debate about its costs and benefits. Fourth Amendment suppression issues appear on virtually every criminal procedure exam.
Landmark Case
Mapp v. Ohio
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