Black-letter propositions
- 01
The exclusionary rule covers primary evidence obtained as a direct result of an illegal search or seizure and also evidence later discovered and found to be derivative of the illegality, such as a statement made at the moment of an unlawful arrest or narcotics found because of that statement.
- 02
Exclusion is not automatic, because the rule applies only where its deterrence benefits outweigh its substantial social costs, and courts have recognized exceptions for independent source, inevitable discovery, and attenuation.
- 03
Under the independent source doctrine, evidence that was first discovered during an unlawful search but was later obtained independently from lawful activities untainted by the initial illegality is admissible.
- 04
A later warrant search is a genuinely independent source only if the officers' decision to seek the warrant was not prompted by what they saw in the illegal entry and the information from the entry was not presented to the magistrate in a way that affected the decision to issue it.
- 05
Under the inevitable discovery exception, evidence is admissible if the prosecution establishes by a preponderance of the evidence that the information ultimately or inevitably would have been discovered by lawful means.
- 06
The prosecution using inevitable discovery does not have to prove that the police acted in good faith, because the rule puts the government in the same position and not a better or worse one than if no illegality had occurred.
- 07
Under the attenuation doctrine, evidence is admissible when the connection between the unconstitutional police conduct and the evidence is sufficiently remote or has been interrupted by an intervening circumstance, and courts weigh the temporal proximity, the intervening circumstances, and the purpose and flagrancy of the official misconduct.
- 08
Discovery of a valid, preexisting, and untainted arrest warrant after an unlawful stop can attenuate the connection between the stop and evidence found in a search incident to the arrest when the officer's error was negligent and not flagrant.
- 09
The Fourth Amendment reasonableness inquiry includes the common-law knock-and-announce principle, but police may dispense with it when there is a threat of violence or a reasonable belief that evidence would be destroyed, and a blanket exception for felony drug investigations is not allowed.
- 10
A violation of the knock-and-announce rule does not require suppression of the evidence found in the search, because the rule protects life, property, and dignity and does not protect against the government seeing or taking evidence described in a warrant.
Use this attack sequence under time
Frame the issue
Identify the illegality and the evidence, and decide whether the evidence is primary or derivative.
Resolve the next checkpoint
Ask whether a source independent of the illegality supplied the same evidence, such as a later warrant not prompted by the illegal entry.
Resolve the next checkpoint
Ask whether the prosecution can show by a preponderance that lawful means would inevitably have found it.
Resolve the next checkpoint
For attenuation, weigh timing, any intervening circumstance such as a valid warrant, and the purpose and flagrancy of the misconduct.
Finish the conclusion
For a knock-and-announce violation, ask what interest the rule protects and remember that suppression is not the remedy.
Common wrong turns
- An officer's later valid warrant does not cure an illegal entry if the decision to get the warrant was prompted by what the officers saw inside.
- Inevitable discovery does not need proof that the police acted in good faith.
- A valid preexisting arrest warrant that surfaces after an unlawful stop can attenuate the taint when the misconduct was not flagrant.
- A knock-and-announce violation does not lead to suppression of what the warrant authorized the police to seize.
Worked example
Officers with no warrant enter a house, see stolen goods on a table, and leave without touching them. Hours later they obtain a warrant based only on information from an informant that they had before the entry, and they return and seize the goods.
The independent source doctrine can admit the goods because the later warrant search was genuinely independent, meaning the decision to seek the warrant was not prompted by the illegal entry and the entry information was not presented to the magistrate.
Practice this topic
The rule and its exceptions
Wong Sun v. United States held that statements made by the defendant in his bedroom at the time of an unlawful arrest were fruits of the agents' unlawful action and should have been excluded, and that narcotics taken from a third party as a result of those statements were likewise fruits. In Utah v. Strieff the Court described the exclusionary rule as covering primary evidence and evidence later discovered and found to be derivative of an illegality, and noted that exceptions keep its deterrence benefits from being outweighed by its social costs.
Hudson v. Michigan repeated that the exclusionary rule applies only where its deterrence benefits outweigh its substantial social costs and that but-for causation can be too attenuated to justify exclusion.
Independent source and inevitable discovery
Murray v. United States held that the Fourth Amendment does not require suppression of evidence initially discovered during an illegal entry if it is also discovered during a later search under a valid warrant wholly independent of the illegal entry. The ultimate question is whether the warrant search was a genuinely independent source, which it is not if the agents' decision to seek the warrant was prompted by what they saw or if information from the entry was presented to the magistrate and affected the decision to issue the warrant.
Nix v. Williams recognized the inevitable discovery exception, under which the prosecution must show by a preponderance of the evidence that the information ultimately or inevitably would have been discovered by lawful means, there a search by volunteers that was already under way. The Court held that the prosecution need not prove the absence of bad faith, because that would put the police in a worse position than if no unlawful conduct had occurred.
Attenuation and knock-and-announce
Brown v. Illinois held that a confession following an illegal arrest is not cured by Miranda warnings alone, and that the temporal proximity of the arrest and the confession, the presence of intervening circumstances, and particularly the purpose and flagrancy of the official misconduct are relevant, with the voluntariness of the statement a threshold requirement and the burden on the prosecution. Utah v. Strieff applied the same three factors and held that a valid preexisting arrest warrant discovered after an unlawful stop attenuated the connection to the evidence found in a search incident to arrest, because the officer's conduct was at most negligent.
Wilson v. Arkansas held that the common-law knock-and-announce principle forms part of the Fourth Amendment reasonableness inquiry. Richards v. Wisconsin held that there is no blanket exception for felony drug investigations, and that the requirement can give way where there is a threat of physical violence or a reasonable belief that evidence would be destroyed. Hudson v. Michigan held that a violation of the rule does not require suppression of the evidence found in the search.
Frequently asked questions
What is the controlling rule for fruit of the poisonous tree: independent source, inevitable discovery, attenuation, and knock-and-announce?+
Name the illegality, classify the evidence as primary or derivative, then test the three exceptions in turn and state which rule applies to the facts.
What is the fruit of the poisonous tree?+
Evidence derived from an unconstitutional search, arrest, or interrogation, which the exclusionary rule generally bars unless an exception applies, as in Wong Sun.
What is the independent source doctrine?+
Evidence first found in an illegal search is admissible if it was later obtained independently from lawful activities untainted by the illegality, as in Murray.
What must the prosecution prove for inevitable discovery?+
By a preponderance of the evidence, that lawful means would ultimately or inevitably have discovered the evidence, under Nix v. Williams.
What factors decide attenuation?+
Temporal proximity, intervening circumstances, and the purpose and flagrancy of the misconduct, under Brown v. Illinois and Utah v. Strieff.
Does a knock-and-announce violation require suppression?+
No, the Court held in Hudson v. Michigan that suppression is not required, because the rule does not protect against the seizure of evidence described in a warrant.