Fruit of the Poisonous Tree

Definition / Rule

The “fruit of the poisonous tree” doctrine extends the Exclusionary Rule to secondary (derivative) evidence obtained as a result of a primary constitutional violation. If the initial illegality is the “poisonous tree,” all evidence that flows from it — confessions, witnesses, physical evidence — is the “fruit” and is presumptively inadmissible. The doctrine was articulated in Silverthorne Lumber Co. v. United States (1920) and the phrase “fruit of the poisonous tree” coined in Nardone v. United States (1939).

Elements

For the fruit of the poisonous tree doctrine to apply:

1. Primary constitutional violation — an underlying Fourth (or Fifth/Sixth) Amendment violation occurred
2. Causal connection — the challenged evidence was obtained by exploiting the primary violation (but for the violation, the evidence would not have been obtained in that manner)
3. No exception applies — none of the three established exceptions breaks the causal chain

The Three Exceptions

1. Independent Source

Evidence that was discovered through a source entirely independent of the constitutional violation is admissible. The government must show that the evidence was in fact obtained through a separate, untainted channel.

• Murray v. United States (1988): Officers conducted illegal warrantless entry, then obtained a valid warrant omitting reference to the illegal entry. Evidence admissible if the warrant application was genuinely independent of the initial illegality.

2. Inevitable Discovery

Evidence is admissible if the government can prove by a preponderance that it would inevitably have been discovered through lawful means, even without the constitutional violation.

• Nix v. Williams (1984): Murder victim’s body, discovered as result of unconstitutional interrogation, admissible because search teams would inevitably have found it through an ongoing lawful search.

3. Attenuation

The fruit may be admissible when the connection between the illegal police conduct and the discovery of the evidence has become so attenuated as to dissipate the taint.

• Wong Sun v. United States (1963): Defendant who was unlawfully arrested, released, and later voluntarily returned to make a statement — statement admissible because the causal chain was attenuated by intervening voluntary act.
• Utah v. Strieff (2016): Evidence from search incident to arrest admissible even though the initial stop was unlawful; pre-existing valid arrest warrant was a critical intervening circumstance. Factors: temporal proximity of the illegality to the discovery, intervening circumstances (the warrant), and flagrancy of police misconduct.

Key Cases

• Silverthorne Lumber Co. v. United States (1920) — Origin of the doctrine; illegally seized documents cannot be used even in their “derivatives.”
• Nardone v. United States (1939) — Justice Frankfurter coined “fruit of the poisonous tree.”
• Wong Sun v. United States (1963) — Established the attenuation exception; created the test of whether evidence “has been come at by exploitation of that illegality or instead by means sufficiently distinguishable.”
• Nix v. Williams (1984) — Established the inevitable discovery exception.
• Utah v. Strieff (2016) — Applied attenuation factors; pre-existing arrest warrant decisive.

Policy

Deterrence: Suppressing derivative evidence removes any incentive for police to conduct initial unconstitutional searches. Without FOTP, officers could conduct illegal searches to identify leads, then manufacture an independent basis for obtaining the evidence.

Costs: Suppression of derivative evidence imposes heavy social costs — guilty defendants go free based on violations that may be attenuated from the ultimate evidence. The three exceptions attempt to balance deterrence against these costs.