Last Updated on: 2nd June 2023, 05:32 pm

The Fruit of the Poisonous Tree Doctrine is a legal rule recognized by the Supreme Court of the United States. The doctrine basically holds that, where the source of evidence is tainted due to unconstitutional conduct on the part of the police, then the evidence discovered as a result of that tainted source is also tainted and inadmissible in court proceedings, including trials. The Fruit of the Poisonous Tree Doctrine was first established by the Supreme Court in 1920.
The doctrine is part of what is known as the Exclusionary Rule, which holds that, generally, evidence which has been gathered in violation of a person’s Constitutional rights is inadmissible and will not be allowed to be presented in court. Thus, under the Exclusionary Rule, a statement or confession given by a defendant by means of improper police questioning (for instance, in violation of the Miranda Rule), evidence gathered in violation of the warrant requirement of the Fourth Amendment or information learned during an illegal arrest, will not be allowed in court, even if it is relevant to the case.
The Fruit of the Poisonous Tree Doctrine takes the Exclusionary Rule one step further by directing that, where improper police conduct (for instance, an illegal and unconstitutional search or improper questioning of a suspect) leads the police to additional evidence, that additional evidence, called “tainted evidence,” will also be excluded from court and the prosecution may not use the tainted evidence against the defendant. As an example, where police learn of material evidence from statements made during an illegal arrest, in violation of the Miranda rule or during an unlawful search, that evidence is tainted and may be excluded.
However, as with most everything involved in the law, it’s not always that simple. The Fruit of the Poisonous Tree Doctrine is subject to four main exceptions.
The first exception allows the tainted evidence to be admitted in court if it was discovered, in some measure, by means of an untainted source. So, if improper conduct led the police to the tainted evidence, but there was also a second source which led them to the evidence without a constitutional violation, the Exclusionary Rule does not apply to bar that evidence. If, for instance, there was a second, constitutionally proper and independent search done after an earlier, improper search, the source of the evidence could be considered as an independent source, removing the “taint” and making the evidence admissible in court.
The second exception allows admission of the tainted evidence where its discovery was inevitable and would have happened even without the unlawful police conduct. If the court finds that normal and proper investigation by law enforcement would have inevitably led to the discovery of the tainted evidence, it can still be received in court, despite the separate unconstitutional police conduct.
The third exception is what is commonly referred to as the Attenuation Doctrine. If the connection between the discovery of the tainted evidence and the improper or unconstitutional police conduct is too attenuated, weak or too remote, the Fruit of the Poisonous Tree Doctrine will not apply to exclude the tainted evidence at trial. Some of the factors considered by courts in determining whether this exception applies are the length of time and circumstances occurring between the improper police conduct and the discovery of the evidence, the degree of the police misconduct and the nature of the evidence itself.
The final exception, known as the Good Faith Exception, applies where police conduct a search based on a warrant, but that warrant is later found to have been improperly issued. If the police acted in good faith based on the warrant, the Fruit of the Poisonous Tree Doctrine does not apply to exclude evidence discovered by the police relying on that warrant. The Good Faith Exception has also been applied to cases where the police have acted on an arrest warrant which, unknown to them, had been earlier quashed or cancelled. Under this exception, evidence gathered in a search following execution of that warrant may not be subject to exclusion under the Fruit of the Poisonous Tree Doctrine.