A search warrant is an order signed by a judge that authorizes police officers to search for specific objects or materials at a definite location at a specified time. For example, a warrant may authorize the search of "the premises at 11359 Happy Glade Avenue between the hours of 8 A.M. to 6 P.M.," and direct the police to search for and seize "cash, betting slips, record books and every other means used in connection with placing bets on horses."

Police officers obtain warrants by convincing a judge or magistrate that they have "probable cause" to believe that criminal activity is occurring at the place to be searched or that evidence of a crime may be found there. Usually, the police provide the judge or magistrate with information in the form of written statements under oath, called "affidavits," which report either their own observations or those of private citizens or police undercover informants. In many areas, a judicial officer is available 24 hours a day to issue warrants. If the magistrate believes that the affidavit establishes probable cause to conduct a search, he or she will issue a warrant. The suspect, who may be connected with the place to be searched, is not present when the warrant issues and therefore cannot contest the issue of probable cause at that time. However, the suspect can later challenge the validity of the warrant before trial.

What Is Probable Cause?

The Fourth Amendment doesn't define "probable cause." Its meaning remains fuzzy. What is clear is that after 200 years of court interpretations, the affidavits submitted by police officers to judges have to identify objectively suspicious activities rather than simply recite the officer's subjective beliefs. The affidavits also have to establish more than a "suspicion" that criminal activity is afoot, but do not have to show "proof beyond a reasonable doubt."

The information in the affidavit need not be in a form that would make it admissible at trial. However, the circumstances set forth in the affidavit as a whole should demonstrate the reliability of the information. In general, when deciding whether to issue a search warrant, a judicial officer will likely consider information in an affidavit reliable if it comes from any of these sources:

• a confidential police informant whose past reliability has been established or who has firsthand knowledge of illegal goings-on
• an informant who implicates herself as well as the suspect
• an informant whose information appears to be correct after at least partial verification by the police
• a victim of a crime related to the search
• a witness to the crime related to the search, or
• another police officer.

Sometimes the police provide mistaken information in the affidavit and the judge or magistrate issues a warrant under circumstances that, given the true state of affairs, would not justify a search under the Fourth Amendment. The question then arises as to whether the search itself is legal. In most situations the search will be upheld if the police acted in good faith when seeking the warrant (that is, they didn't know about the mistakes in the affidavit). The reasoning here is that:

• it makes no sense to condemn the results of a search when police officers have done everything reasonable to comply with Fourth Amendment requirements, and
• the purpose of the rule excluding the results of an invalid search as evidence is to curb the police, not a judge, and that if a judge makes a mistake it should not be grounds to exclude evidence.

What Police Can Search for and Seize Under a Warrant

The police can search only the place described in a warrant, and usually can seize only the property that the warrant describes. The police cannot search a house if the warrant specifies the backyard, nor can they search for weapons if the warrant specifies marijuana plants. However, this does not mean that police officers can seize only those items listed in the warrant. If, in the course of their search, police officers come across contraband or evidence of a crime that is not listed in the warrant, they can lawfully seize the unlisted items.

If the warrant specifies a certain person to be searched, the police can search only that person unless they have independent probable cause to search other persons who happen to be present at the scene of a search. However, if an officer has a reasonable suspicion that an onlooker is engaged in criminal activity, the officer can question the onlooker and, if necessary for the officer's safety, conduct a frisk for weapons.

Technically, a person may require the police to produce a warrant before admitting them into his or her home for a search. However, people sometimes run into trouble when they "stand on their rights" in this way. A warrant is not always legally necessary, and a police officer may have information of which a person is unaware that allows the officer to make a warrantless entry. If an officer announces an intention to enter without a warrant, a person should not risk injury or a separate charge of "interfering with a police officer." Rather, the person should stand aside, let the officer proceed and allow a court to decide later whether the officer's actions were proper. At the same time, the person should make it clear that he or she does not consent to the search.

When Search Warrants Aren't Required

Most searches occur without warrants being issued. Over the years, the courts have defined a number of situations in which a search warrant is not necessary, either because the search is per se reasonable under the circumstances or because, due to a lack of a reasonable expectation of privacy, the Fourth Amendment doesn't apply at all.

Consent Searches

If the person in control of the premises to be searched freely and voluntarily agrees to the search, the search is valid and whatever the officers find is admissible in evidence. Police officers do not have to warn people that they have a right to refuse consent to a search. To constitute a valid consent to search, the consent must be given "freely and voluntarily." If a police officer wrangles a consent through trickery or coercion, the consent does not validate the search. Often, a defendant challenges a search on the ground that consent was not voluntary, only to have a police officer testify to a conflicting version of events that establishes a valid consent. In these conflict situations, judges tend to believe police officers unless defendants can support their claims through the testimony of other witnesses. Sometimes people who are intimidated by the police misinterpret the "request" to be a command and will allow the search. However, so long as an officer does not engage in threatening behavior -- such as placing their hand on a sidearm -- judges will not set aside otherwise genuine consents.

Many disputes about consent have to do with who has the right to consent. For example, do parents have a right to consent to a search of their children's rooms? As a general rule, an adult in rightful possession of a house or apartment usually has legal authority to consent to a search of the entire premises. But if there are two or more separate tenants in one dwelling, courts often rule that one tenant has no power to consent to a search of the areas exclusively controlled by the other tenants (for instance, their separate bedrooms). Similarly, a landlord is not considered to be in possession of an apartment leased to a tenant, and therefore lacks authority to consent to a search of leased premises. The same is true for hotel operators. On the other hand, an employer can validly consent to a search of company premises, which extends to an employee's work area, such as a desk and machinery, but not to clearly private areas such as an employee's clothes locker.

A tricky twist is that the consent in these types of cases will be considered valid if the police reasonably believe that the consenting person has the authority to consent, even if it turns out they don't.

The Plain View Doctrine

Police officers do not need a warrant to search and seize contraband or evidence that is "in plain view" if the officer is where he or she has a right to be when the evidence or contraband is first spotted. For instance, the police may search for and seize marijuana growing outdoors if they first spot the marijuana from an airplane or helicopter, since the marijuana is deemed to be in plain view. Similarly, if an officer walks by a car and spots evidence or contraband through the car window, the plain view doctrine applies and a search may be conducted without a warrant. The same rule would apply if an officer is in your home for other valid reasons and spots drugs on a table or cabinet.

Search Made in Connection With an Arrest

Police officers do not need a warrant to make a search "incident to an arrest." After an arrest, police officers have the right to protect themselves by searching for weapons and to protect the legal case against the suspect by searching for evidence that the suspect might try to destroy. Assuming that the officer has probable cause to make the arrest in the first place, a search of the person and the person's surroundings following the arrest is valid, and any evidence uncovered is admissible at trial.
To justify a search as incident to an arrest, a spatial relationship must exist between the arrest and the search. The general rule is that after arrest the police may search a defendant and the area within a defendant's immediate control. For example, an arresting officer may search not only a suspect's clothes, but also the suspect's wallet or purse. If an arrest takes place in a kitchen, the arresting officer can probably search the kitchen, but not the rest of the house. If an arrest takes place outside a house, the arresting officer cannot search the house at all. To conduct a search broader in scope than a defendant and the area within the defendant's immediate control, an officer would have to obtain a warrant. However, the police may make what's known as a "protective sweep" following an arrest. When making a protective sweep, police officers can walk through a residence and make a "cursory visual inspection" of places where an accomplice might be hiding. For example, police officers could look under beds and inside closets. To justify making a protective sweep, police officers must have a reasonable belief that a dangerous accomplice might be hiding inside a residence. If a sweep is lawful, the police can lawfully seize contraband or evidence of crime that is in plain view.

Searches of Cars and Their Occupants

Cars may be searched without a warrant whenever the car has been validly stopped and the police have probable cause to believe the car contains contraband or evidence. The reasons why no warrant is required for a car search are:

• cars are easily moved and may disappear while a warrant is being sought, and
• people driving cars do not have the same expectation of privacy in cars as they do in their homes.

If the police have probable cause to search the car, all compartments and packages that may contain the evidence or contraband being searched for are fair game.

While a police officer cannot search a car simply because the car was stopped for a traffic infraction -- since routine traffic stops are not arrests that would justify a "search incident to an arrest" -- the police can order the driver and any passengers out of the car for safety considerations, even though there is no suspicion of criminal wrongdoing other than the traffic infraction. The police also can "frisk" the occupants for weapons so long as they have a "reasonable suspicion" that the occupants are involved in criminal activity beyond the traffic violation and are reasonably concerned for their safety.

The police are sometimes accused of using technical traffic violations as a pretext for stopping the car for the real reason of conducting a further investigation that often includes a frisk and possible search of the vehicle. Sometimes these types of stops are allegedly based on racial profiling. Whatever the police officer's motives, however, if the officer had a valid reason to stop the vehicle, even a ticky-tack one like a broken rear taillight, the stop is legal. And, if the initial stop is valid, any lawful frisk, search or arrest that follows the stop is also valid.

The Emergency Exception

As a general rule, the police are authorized to make a warrantless search when the time it would take to get a warrant would jeopardize public safety or lead to the loss of important evidence. Here are some situations in which most judges would uphold a warrantless search:

• An officer checks an injured motorist for possible injuries following a collision and finds illegal drugs.
• Following a street drug arrest, an officer enters the house after the suspect shouts into the house, "Eddie, quick, flush our stash down the toilet." The officer arrests Eddie and seizes the stash.
• A police officer on routine patrol hears shouts and screams coming from a residence, rushes in and arrests a suspect for spousal abuse.

In these types of emergency situations, an officer's duty to protect people and preserve evidence outweighs the warrant requirement.

If a judge decides that an officer had time to obtain a search warrant without risking injury to people or the loss of evidence, the judge should refuse to allow into evidence whatever was seized in the course of the warrantless search. Judges always have the final word on whether police officers should have obtained warrants.

Other Searches That May be Made Without A Warrant

The police may search a person's trash put out for collection without a warrant on the ground that, since the trash has been put out in public, there is no longer a reasonable expectation of privacy and the Fourth Amendment doesn't apply.

A backyard may also be searched without a warrant if members of the public can see into it from where they have a right to be. Again, there is no reasonable expectation of privacy in an area that is open to public view. Similarly, fields around a house in a rural area are subject to a warrantless search as long as the police didn't trespass to obtain the information leading to probable cause for the search.

School lockers are subject to warrantless searches as long the school officials have a reasonable basis for conducting the search.