FRUIT OF THE POISONOUS TREE

Fruit of the poisonous tree is a legal metaphor in the United States used to describe evidence gathered with the aid of information obtained illegally. The logic of the terminology is that if the source of the evidence (the "tree") is tainted, then anything gained from it (the "fruit") would be likewise.

Such evidence is not generally admissible in court.For example, if a police officer conducted an unconstitutional (Fourth Amendment) search of a home and obtained a key to a locker in a train station, thus obtaining evidence of a crime from the locker, then that evidence would more than likely be excluded in accordance with the fruit of the poisonous tree doctrine. The discovery of a witness is not evidence in itself because the witness is attenuated by separate interviews, in-court testimony and their own statements.

The doctrine is an extension of the exclusionary rule, which, subject to some exceptions, prevents evidence obtained in violation of the Fourth Amendment from being admitted in a criminal trial. Like the exclusionary rule, the fruit-of-the-poisonous-tree doctrine is intended to deter police from using illegal means to obtain evidence.

The doctrine is subject to three main exceptions. The tainted evidence will be admissible if

(1) it was discovered in part as a result of an independent, untainted source;
(2) it would inevitably have been discovered despite the tainted source; or
(3) the chain of causation between the illegal action and the tainted evidence is too attenuated.

The Fruit of the Poisonous Tree doctrine stems from the 1920 case of Silverthorne Lumber Co. v. United States.

Silverthorne Lumber Co. v. United States, 251 U.S. 385 (1920), was a U.S. Supreme Court Case in which Silverthorne attempted to evade paying taxes. Federal Agents illegally seized tax books from Silverthorne, and created copies of the records. The issue in this case is whether or not derivatives of illegal evidence are permissible in court.

The ruling was that to permit derivatives would encourage police to circumvent the Fourth Amendment, so the illegal copied evidence was held tainted and inadmissible. This precedent is known as Fruit of the Poisonous Tree and is an extension of the exclusionary rule.

The Fruit of the Poisonous Tree phrase is a reference to the biblical passage originally found in Matthew 7:17-20

Mat 7:17 Likewise every good tree bears good fruit, but a bad tree bears bad fruit.

Mat 7:18 A good tree cannot bear bad fruit, and a bad tree cannot bear good fruit.

Mat 7:19 Every tree that does not bear good fruit is cut down and thrown into the fire.

Mat 7:20 Thus, by their fruit you will recognize them.