4th Amendment

"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."

The search-and-seizure provisions of the Fourth Amendment are all about privacy. To honor this freedom, the Fourth Amendment protects against "unreasonable" searches and seizures by state or federal law enforcement authorities.

What you need to know is that the Fourth Amendment does permit searches and seizures that are "reasonable."

In practice, this means that the police may override your privacy concerns and conduct a search of you, your home, barn, car, boat, office, personal or business documents, bank account records, trash barrel, or whatever, if "...the police have probable cause to believe they can find evidence that you committed a crime, and a judge issues a warrant, or the particular circumstances justify the search without a warrant first being issued."

The Fourth Amendment applies to a search only if a person has a "legitimate expectation of privacy" in the place or thing searched. If not, the amendment offers no protection because there are, by definition, no privacy issues.

Courts generally use a two-part test fashioned by the U.S. Supreme Court to determine whether, at the time of the search, a defendant had a legitimate expectation of privacy in the place or things searched:

Test 1: Did the person have an expectation of some degree of privacy?

Test 2: Is the person's expectation objectively reasonable, that is, one that society is willing to recognize?

For example, a person who uses a public restroom expects not to be spied upon (the person has an expectation of privacy), and most people -- including judges -- would consider that expectation to be objectively reasonable. Therefore, the installation of a hidden video camera by the police in a public restroom would be considered a "search" and would be subject to the Fourth Amendment's requirement of reasonableness.

On the other hand, if an officer stops a car and, when talking to the driver, happens to notice a loaded .45 on the passenger seat, there's been no search under the Fourth Amendment. That's because, even if the driver somehow considered the passenger seat to be a private place, society isn't willing to extend privacy protections to that particular location. In other words, there's no objectively reasonable expectation of privacy with respect to the gun because it was "in plain view."

A good example of how this works comes from a U.S. Supreme Court case in which the court held that a bus passenger had a legitimate expectation of privacy in an opaque carry-on bag positioned in a luggage rack above the passenger's head. The Court held that the physical probing by the police of the bag's exterior for evidence of contraband constituted a search subject to Fourth Amendment limitations. (Bond v. U.S., 529 U.S. 334 (2000).)

Private security personnel have at times outnumbered police officers in the United States by three to one. As a result, whether you're shopping in a supermarket or a pharmacy, working in an office building, or visiting a friend in a housing project, you may be more likely to be confronted by a security guard than by a police officer. The Fourth Amendment doesn't apply to searches carried out by non-governmental employees, like private security guards, who aren't acting on the government's behalf.

For example, assume that a shopping mall security guard acting on a pure hunch searches a teenager's backpack. Inside the backpack the guard finds a baggie containing an illegal drug. The guard can detain the teenager, call the police, and turn the drug over to a police officer. The drug is admissible in evidence, because the search was conducted by a private security guard acting on his own, rather than at the officer's direction.

The "exclusionary rule" applies if, upon review, a court finds that an unreasonable search occurred, any evidence seized as a result of it cannot be used as direct evidence against the defendant in a criminal prosecution. This principle, established by the U.S. Supreme Court in 1961, has come to be known as the exclusionary rule.

To this day, many commentators criticize the exclusionary rule on the ground that it unfairly "lets the criminal go free because the constable has erred," but the rule's supporters argue that excluding illegally seized evidence is necessary to deter police from conducting illegal searches. According to this deterrence argument, the police are less likely to conduct improper searches if the resulting evidence can't be used to convict the defendant.

Fruit of the poisonous tree doctrine. Not only is evidence that's the product of an illegal search generally inadmissible in court, but so too is additional evidence that derived from the initial evidence. This principle is colorfully known as the "fruit of the poisonous tree" doctrine. The "tree" is the evidence that the police illegally seize in the first place; the "fruit" is the second-generation product of the illegally seized evidence. Both tree and fruit are typically inadmissible at trial.

To learn more about search-and-seizure law, get The Criminal Law Handbook: Know Your Rights, Survive the System, by Paul Bergman (Nolo).