Fruit of the Poisonous Tree

Fruit of the Poisonous Tree

The exclusionary rule described above would accomplish little if it reached only the item officers pulled from a room during an illegal search. An officer who cannot use the seized object can still use whatever it revealed, such as a name, an address, a confession it prompted, or a witness it identified. If those leads stayed available, one unlawful search could be converted into a prosecution built entirely from its consequences, and the deterrent effect on which the modern rule rests would disappear. The fruit of the poisonous tree doctrine closes that gap by treating evidence derived from an illegal search, arrest, or interrogation as inadmissible, because the original illegality (the poisonous tree) taints what grows from it (the fruit).¹

Two terms organize everything that follows. Primary evidence is what officers obtain directly through the unconstitutional act, such as drugs found in a home searched without a warrant. Derivative evidence is what the police find later, as an indirect result of that act, by following what the primary evidence or the illegality itself revealed. In Utah v. Strieff the Court restated that the exclusionary rule encompasses both "primary evidence obtained as a direct result of an illegal search or seizure" and "evidence later discovered and found to be derivative of an illegality."² The standard illustration is a map seized in an illegal search that shows where a murder weapon lies hidden: the map is primary evidence, and the weapon found by following it is derivative evidence that is equally inadmissible.³ The doctrine covers physical and testimonial evidence alike, so a statement can be fruit just as an object can.⁴

The metaphor comes from Nardone v. United States, where the Court held that a federal ban on wiretap evidence reached not only the intercepted conversations but also evidence derived from exploiting them.⁵ The government's first convictions in that case had been reversed because they rested on intercepted telephone messages obtained in violation of § 605 of the Communications Act of 1934. At the retrial the Court of Appeals read the statute to bar only the exact words heard over the taps, leaving the government free to make every other use of what the taps revealed.⁶ The Supreme Court rejected that reading for a practical reason: forbidding the direct use of a method while putting no curb on its indirect use would invite the very methods the ban condemned.⁷ An officer who may not introduce the overheard words but may freely exploit them still profits from the tap, so a ban confined to the words would restrain nothing.

The Court drew on Silverthorne Lumber Co. v. United States, which had reasoned that a provision forbidding the acquisition of evidence in a certain way means that the evidence "shall not be used at all."⁸ The same passage marks the doctrine's edge, because facts the government learned by its own wrong do not become "sacred and inaccessible," and if they are learned from an independent source they may be proved like any others.⁹ That qualification foreshadows the independent source doctrine taught later in this chapter. Nardone construed a statute, and Wong Sun v. United States applied the same reasoning to an unlawful entry and arrest under the Fourth Amendment, requiring exclusion of evidence obtained as a direct or indirect result of an unconstitutional search or arrest.¹⁰

The decisions that give the doctrine its reach also supply its limit. A rule excluding everything with any causal link to the violation would leave the prosecution worse off than if the officers had never erred, because evidence the illegality did not truly help produce would be lost along with evidence it did. Wong Sun therefore declined to treat all evidence as fruit simply because it would not have come to light but for the illegal police action, and asked instead whether, granting the primary illegality, the evidence was "come at by exploitation of that illegality or instead by means sufficiently distinguishable to be purged of the primary taint."¹¹ A causal link to the violation is where the inquiry starts, and the exploitation question is where it ends. Students lose this issue when they treat every causal link to the violation as poisoning the evidence.¹²

The two subsections below take these halves in order. The first shows through Wong Sun how a statement taken after an unlawful entry, and the evidence the agents located by following it, both fall within the doctrine's reach, and the second develops the limiting question. The exceptions that turn on the causal link, which Strieff identifies as independent source, inevitable discovery, and attenuation, follow after them.¹³

Direct and Derivative Evidence

The previous section established that suppression reaches beyond the item police seize, and this subsection shows what that reach looks like on real facts. Wong Sun v. United States serves as the running example because a single illegal entry there produced two different kinds of evidence at two different distances from the violation.¹⁵ Federal agents broke a door and followed Toy into the bedroom where his wife and child were sleeping, and the Court upheld the finding that the uninvited entry and the bedroom arrest that followed were unlawful.¹⁶ Six or seven officers took part, and Toy was almost immediately handcuffed.¹⁷ In the bedroom he made statements, and those statements led the agents to Yee, from whom they took narcotics. The doctrine therefore has to say what becomes of the statement and what becomes of the drugs.

Toy's bedroom statement is the nearer item. It followed the forced entry and handcuffing so immediately that the Court treated it as fruit of the official illegality, just as it would treat a tangible object seized in an unlawful search.¹⁸ Some classifications label a confession given after an illegal arrest as derivative, since it follows the arrest rather than being taken in it, and the label has no effect on admissibility because the rule excludes primary and derivative evidence alike.¹⁹ What the label does change is the inquiry. Primary evidence is excluded once the violation is shown, subject to the limits on the rule itself taught later in this chapter, whereas derivative evidence raises the further question whether it is actually tainted by the earlier violation, and that question is the subject of the next subsection.²⁰

The narcotics sit one step further out, since the chain ran from the entry to the statement and from the statement to the drugs. The prosecutor candidly told the trial court, "we wouldn't have found those drugs except that Mr. Toy helped us to."²¹ The Court held that the narcotics could not be used against Toy, whose home had been invaded, because the government had not learned of them from an independent source and the link between the lawless conduct and the discovery had not weakened.²² The principle underneath is the one the Court drew from Silverthorne Lumber Co. v. United States: the prohibition on using illegally acquired evidence extends to the indirect products of an invasion as well as the direct ones.²³ Why these facts fell on the excluded side, and how a prosecutor can break a chain of this kind, is the work of the next subsection and of the independent source, inevitable discovery, and attenuation sections that follow.

Wong Sun also settles that the form of the evidence does not matter. The Court reasoned that the Fourth Amendment may protect against the overhearing of verbal statements as well as the seizure of papers and effects, that testimony about matters observed during an unlawful invasion had already been excluded, and that verbal evidence deriving so immediately from an unlawful entry and arrest is no less fruit than the more common tangible kind.²⁴ The reason is an incentive problem. If only objects counted as fruit, officers who had entered a home unlawfully would have every reason to leave the objects alone and press the occupant for statements and leads, and the violation would pay off anyway. The Court framed the point through the rule's two purposes, concluding that relaxing the rule for verbal evidence would endanger both the deterrence of lawless conduct by officers and the closing of the courts to evidence unconstitutionally obtained.²⁵

A related argument fared no better. The government contended that Toy's statements were ostensibly exculpatory, and the Court answered that they soon proved incriminating by leading to the evidence, and that in circumstances like these it is immaterial whether the declarations are called exculpatory.²⁶ The reach of the rule can therefore be summarized in layers: tangible materials seized in an unlawful search, testimony about knowledge acquired during it, and derivative evidence of both tangible and testimonial kinds, up to the point at which the connection with the violation becomes so attenuated as to dissipate the taint.²⁷

The doctrine is also not tied to the Fourth Amendment. It began in Nardone v. United States with a statutory violation, the interception of telephone messages in breach of § 605 of the Communications Act of 1934, and the Court held there that the ban reached evidence derived from exploiting the messages as well as the messages themselves.²⁸ Wong Sun then applied the same reasoning to an unlawful entry and arrest. In Nix v. Williams the Court recorded that the doctrine has been applied where the violation was of the Sixth Amendment as well as of the Fifth, and it identified the common rationale as deterrence: exclusion is needed to deter police from violating constitutional and statutory protections, and the prosecution is not to be put in a better position than it would have occupied had no illegality occurred.²⁹ The Sixth Amendment version appears in United States v. Wade, where the Court applied the Wong Sun test to the in-court identifications of witnesses who had viewed the defendant at a lineup held without his counsel, and sent the case back for a determination whether those identifications had an origin independent of the lineup.³⁰

Because the doctrine follows the deterrence rationale, the chain does not carry from every violation to every product. A plurality in United States v. Patane declined to suppress a pistol located through an unwarned but voluntary statement, reasoning that the Miranda rule protects the Self-Incrimination Clause, that the clause is not implicated by admitting physical evidence resulting from voluntary statements, and that a mere failure to warn leaves nothing to deter.³¹ Toy's statement differs because it came out of an unlawful entry and arrest, a Fourth Amendment violation that exclusion exists to deter, and the heroin inherited that taint through the statement. Students lose this issue when they carry the poisonous-tree chain from a missing Miranda warning to the physical evidence it produced, because the chain stops where the statement was voluntary.

But-For Causation Is Not Enough

The previous subsection traced suppression from the statement Toy made in his bedroom to the narcotics that statement led agents to, and that chain of cause and effect invites an overreading. If every item with a causal link to the violation were excluded, the doctrine would sweep in evidence the illegality never truly helped the police obtain. Wong Sun v. United States supplies the boundary in the same passage that excludes the narcotics. The Court declined to hold that all evidence is fruit simply because it would not have come to light but for the illegal actions of the police, and asked instead whether the evidence was come at by exploitation of the illegality or by means sufficiently distinguishable to be purged of the primary taint.³⁴ In Hudson v. Michigan the Court restated the point in the vocabulary of logic, observing that but-for causality is "only a necessary, not a sufficient, condition for suppression."³⁵ A necessary condition is one without which the claim fails, so evidence the illegality did not help produce at all cannot be fruit. A sufficient condition would end the inquiry as soon as the link was shown, and the Court has refused to give the link that effect.

The limit rests on two separate reasons. The first concerns the position the rule leaves the prosecution in. Exclusion exists to keep the police from profiting from their own violation, so the prosecution is not to be put in a better position than it would have occupied had no illegality occurred, and the same reasoning forbids putting it in a worse position because of an earlier police error.³⁶ A pure but-for test would break that balance, since a link that is real but runs through a path the police did not control would cost the prosecution evidence the violation did not help it obtain. An officer deciding whether to cut a corner weighs what the corner will buy, and where the violation buys nothing that lawful work would not also have delivered, exclusion has no conduct to correct. The second reason concerns fit. The penalty imposed on the government and the public must bear some relation to the purposes of the constitutional rule that was violated, so when suppression would serve none of those purposes, a causal link does not carry the evidence out of the courtroom.³⁷

The narcotics taken from Yee show the rule on the excluded side. The prosecutor conceded that the agents would not have found the drugs except for Toy's help, and that concession established the causal link.³⁸ The Court did not stop there. It added that the government had not learned of the drugs from an independent source and that the connection between the lawless conduct and the discovery had not weakened, and on that basis it held that the drugs were come at by exploitation of the illegality and could not be used against Toy.³⁹ The concession therefore supplied the first half of the analysis, and the absence of any distinguishable path supplied the second.

Wong Sun's own statement sits on the other side of the line with a causal link just as strong. He was also illegally arrested, and days later he voluntarily returned to the station and confessed. The Court noted that he would not have confessed but for the illegal actions of the police, yet the police had not exploited the arrest to obtain the statement, so it was obtained by means sufficiently distinguishable from the violation and could be admitted.⁴⁰ Because the drugs and the later statement share a causal link to an unlawful arrest, the link cannot be what separates them, and the difference lies in the route. Toy's statements and the narcotics followed the lawless entry at once, in a bedroom filled with officers after he was handcuffed, while Wong Sun came back by his own choice after time had passed.⁴¹

The causal link can also be missing altogether. In Hudson officers held a valid warrant to search for drugs and firearms, knocked, and entered after waiting perhaps three to five seconds, and the Court held that the exclusionary rule does not apply to that knock-and-announce violation.⁴² Part of the reasoning was causal. The illegal manner of entry was not a but-for cause of finding the evidence, because the police would have executed the warrant and found the gun and drugs whether or not the preliminary misstep had occurred.⁴³ The Court then added that even if the entry could be called a but-for cause, the evidence would not be fruit for that reason alone.⁴⁴ The deterrence-based treatment of knock-and-announce violations comes later in this chapter. What matters here is that the Court treated the causal link first as a threshold the evidence must cross and then as a link that may still be too weak to justify exclusion.

A real causal link can also be too weak when suppression would not serve the purpose of the violated rule. In New York v. Harris the police made an illegal warrantless arrest inside Harris's home, and the Court held that suppressing a statement he later gave outside the house would not serve the rule that made the in-home arrest illegal. That rule protects the home, and anything incriminating that the police gathered from arresting him there rather than elsewhere had already been excluded.⁴⁵ The statement was connected to the arrest, yet it came in. The exploitation question is also the general test and is not confined to arrests, which is why the Court adopted it for in-court identifications by witnesses who had attended a lineup held without the defendant's counsel.⁴⁶

The twin shows what the analysis is tracking. Students lose this issue when they stop at a stem's statement that police would not have found the evidence without the violation, because that statement establishes only the causal link and leaves the exploitation question open.⁴⁷ The same stem may also supply facts that answer the question, such as days passing, a free decision by the defendant, or a lawful route to the evidence, and the evidence then comes in.

The fourth step is the doorway to those sections. Each one shows sufficiently distinguishable means in a different way: the independent source doctrine shows that a lawful channel unconnected to the violation produced the evidence, inevitable discovery shows that lawful means would ultimately have produced it, and attenuation shows that the connection to the illegality has weakened until the taint is dissipated.⁴⁸