A cornerstone of the protections against illegal searches of your person and seizure of your property and yourself by the police — protections established by the Fourth Amendment to the U.S. Constitution — is that any evidence that the police might collect against you as the result of such an illegal search can be kept out of a criminal trial against you under what is known as the “fruit of the poisonous tree” doctrine. This doctrine is not, however, an ironclad defense against the use of otherwise illegally gathered evidence. Courts have carved out some exceptions to the general rule, one of which is “attenuation.”

How does attenuation work?

Before we look at the attenuation rule, let’s first examine how the fruit of the poisonous tree doctrine precludes the use of improperly-obtained evidence from a police search. Let’s say that you are visiting a friend’s house that the neighbors suspect is being used as a place to buy and sell illegal drugs. The police react to the neighbor complaints by putting the house under surveillance, hoping to observe that kind of activity as the pretext to apprehend people involved in illegal drug transactions. As you are leaving that house, a police officer stops you and conducts a search of your person. If he finds something that suggests that you have participated in criminal activity, can he use that evidence?

The fruit of the poisonous tree doctrine would normally answer “No” to that question if all the police officer had to base his search on was seeing you leave the house: by itself that ordinarily would not be behavior on your part that would raise a reasonable level of suspicion on the part of the officer to justify stopping and searching you.

But what happens if during the stop the police officer learns that you are the subject of an outstanding arrest warrant for some other alleged crime, like a traffic violation? What effect might this have on bypassing the fruit of the poisonous tree doctrine and allowing the otherwise illegally seized evidence against you? This is where the attenuation rule can come into play.

The hypothetical above is based on actual events that led to drug-related charges against an individual when the officer who searched him after he left a suspected drug house learned that there was an outstanding warrant for his arrest based on a separate alleged incident of criminal conduct. The search revealed quantities of illegal drugs and drug paraphernalia, and that led to the man’s arrest. The accused sought to have that evidence excluded from trial based on the fruit of the poisonous tree doctrine.

The state supreme court where the arrest took place sided with the defendant and ordered the drug evidence suppressed. The prosecution had argued that the attenuation rule applied because the items that the police officer found during the search were found not as a result of the questionable stop after leaving the house, but rather because of the arrest warrant the officer found out about (that is, even if the stop and search was otherwise improper, the separate warrant was the basis of the search and was far enough removed — “attenuated” — from the stop that the fruit of the poisonous tree doctrine did not apply.

The case eventually went all the way to the U.S. Supreme Court, which recently ruled in a 5-3 decision that the state supreme court wrongly prevented the prosecution from using the attenuation rule to keep the drugs and paraphernalia as evidence. The Court’s majority reasoned that as long as the search was based on a lawful search at the time of an arrest (based on the outstanding arrest warrant), and as long as the improper stop of the accused was an isolated incident and not part of a pattern of wrongful searches and seizures by the police, the attenuation rule properly applied to this situation.

How can the attenuation rule affect you?

The Constitutional prohibition against illegal searches and seizures by police, and the various exceptions to it (the attenuation rule is but one) depend on the facts of each case. The most important thing you can do to use these rules in your favor is to have a defense attorney on your side who knows not only the applicable federal and state laws and court cases that apply to searches and seizures, but also has the experience to match up the facts of your case to those laws and court decisions to identify the best ones to argue on your behalf.