Policing | Section 3.2

Fundamentals of Policing by Adam J. McKee

This content is released as a draft version for comment by the scholarly community.  Please do not distribute as is. 

The Fourth 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 Fourth Amendment is extremely important because it covers both searches and seizures.  That means that almost all physical evidence must be gathered in a way that passes Fourth Amendment standards (as interpreted by the Federal courts).  In addition, the courts consider an arrest as a seizure of the person, and thus the Fourth Amendment applies to arrests as well.

The original text of the Fourth Amendment (see above) can be misleading if one takes a literal approach to understanding what is prohibited. 

The phrase “persons, houses, papers, and effects” suggest that the Fourth Amendment protects property.  Under the common law of England and under United States law for a very long time, that is exactly what was protected. The Court later rejected this approach because it did not fit well into the modern world.  The court said in Katz v. United States (1967),

“The premise that property interests control the right of the Government to search and seize has been discredited. . .. We have recognized that the principal object of the Fourth Amendment is the protection of privacy rather than property, and have increasingly discarded fictional and procedural barriers rested on property concepts.”

From Katz forward, any new technology that came along and could be involved in a search would be tested against a reasonable expectation of privacy.  Homes (a term that the courts have applied to almost any dwelling) would still be of critical importance because a person usually has a reasonable expectation of privacy in the home.


Under the common law tradition, it was lawful to arrest a person who had committed a “breach of the peace” or a felony without a warrant.   This common law history is reflected in the modern procedural rule that an arrest can be made in a public place on probable cause, regardless of whether a warrant has been obtained. In contrast, in order to make an arrest in the suspect’s home, police officers must have a warrant.  Exceptions, such as exigent circumstances, have been carved out by the courts. The Fourth Amendment applies to ”seizures” of the person, and it is not necessary that a detention be a formal arrest to invoke the protections of the Fourth Amendment.

Until recently (the Civil Rights Revolution of the Warren Court), the legality of arrests was seldom heard by the Supreme Court because of the long-standing rule that a person detained by an arbitrary seizure (unlike evidence obtained as a result of an unlawful search) remained subject to custody and presentation to court.  In other words, there was no exclusionary rule that applied to illegal arrests like there was for illegally obtained evidence. Recently, however, the courts have reconsidered this provision. By the application of self-incrimination and other exclusionary rules to the States, the high courts have determined that verbal evidence, confessions, and other admissions, can be excluded from evidence.

A police officer can make a lawful arrest when he or she has an arrest warrant.  Having a warrant provides the officer with legal protection. Thus, arrest should be made with warrants whenever possible.  Generally, an officer does not have to have physical custody of the warrant. Knowledge amounting to probable cause to believe such a warrant exists is generally sufficient.  Arrests are frequently made based on warrant checks when an officer “runs” a suspect’s record via radio during traffic stops and other citizens encounters.

A bench warrant is a variant of an arrest warrant issued by a judge, commanding all law enforcement officers to arrest the named person on sight.  Such warrants are issued when a judge deems a person to be in contempt of court, often for failure to appear at an appointed time for a mandatory hearing.   

Probable Cause

Probable cause is critical to understand the requirements of the Fourth Amendment, yet the Amendment makes no effort to define the term.  It is easy to say that it is an evidentiary standard, falling somewhere above a mere hunch, and coming up short of the beyond a reasonable doubt standard used at criminal trial.  Modern definitions are entirely judicial constructs, handed down by judges in various cases.  

In Draper v. United States (1959) the court made this clarification:  ”In determining what is probable cause . . . we [the Court] are concerned only with the question whether the affiant had reasonable grounds at the time of his affidavit . . . for the belief that the law was being violated on the premises to be searched; and if the apparent facts set out in the affidavit are such that a reasonably discreet and prudent man would be led to believe that there was a commission of the offense charged, there is probable cause….”   

The courts most commonly use a totality of the circumstances analysis to determine if probable cause exists.  This means that no particular type of evidence is given paramount consideration.  Everything is taken together. A totality of the circumstances test means that there is no single deciding factor that the court will consider.  In other words, the magistrate will consider all the facts and the context and then conclude from the whole picture whether probable cause exists.

The reasonable man, a construct used frequently by the courts, usually comes down to the opinion of a judge (or sometimes a jury) in practice.  Unfortunately, the test is always a subjective one.  An officer’s opinion about probable cause may not be shared by a judge later on, and evidence could be suppressed.  Agreement by a neutral, detached magistrate goes a long way in supporting the officer’s argument later that he indeed had probable cause.  This is the primary reason that I make the frequent warning: If at all possible, get a warrant.  

A major requirement for probable cause is that it be based on trustworthy information.  Information known to the officer (what she personally saw or heard) or known to another officer is generally considered trustworthy.  Information learned from average citizens may well be considered trustworthy. When it comes to the use of confidential informants by police, there is no assumption of trustworthiness.  In other words, when informants are used, the courts want more evidence to support the informant’s statements. In other words, the police must generally have other information that corroborates the informant’s version of things.  In addition, the informant’s record for providing trustworthy information may be taken into account.


An applicant for a warrant must present to the magistrate facts sufficient to enable the officer himself to make a determination of probable cause.  The rule here is that if it isn’t on paper, it didn’t happen.  In other words, all of the facts necessary to support a finding of probable cause must be in the affidavit.  An affidavit (in support of a warrant application) is a sworn statement, made by the officer requesting the warrant, attesting to the facts that will be used by the magistrate to determine if probable cause exists.

Like with a search warrant, an officer must establish probable cause to obtain an arrest warrant.  Recall that the courts regard an arrest as a seizure of the person, thus the protection against unreasonable searches and seizures applies to arrest warrants as well as search warrants.

For a warrant to be valid, it must be issued by a neutral, detached magistrate.  The courts often use the term disinterested.  Do not confuse the term disinterested with uninterested.  Disinterest speaks to neutrality, not to the fact that the magistrate is unconcerned with the outcome.  It means that the judge isn’t rooting for the cops or the suspect, but that she is interested in a fair, impartial determination of whether the officer has enough information (evidence) to convince a reasonable person that the suspect has likely committed a crime.

The idea of the magistrate requirement is not to say that police officers are ‘shady’ and cannot be trusted.  The idea is for the courts to accept the fact that police officers are in the business of catching “bad guys,” and they may be a little overzealous in determining when in a citizen has stepped over the line into “bad guy” territory.

Another important legal requirement for a warrant is the particularity requirement.  As the text of the Fourth Amendment says the person or place to be searched and the things to be seized must be particularly described.  Particularity can be considered as synonymous with specificity.  In other words, a warrant must be specific.  There should be no question as to which person is to be searched or arrested, or, in the case of a home, which place should be searched.

Items Subject to Seizure

Broadly speaking, three categories of things can always be seized pursuant to a warrant:

Contraband:  Things that are in themselves illegal to possess, such as narcotics, weapons, explosives and so forth.

Fruits of crime:  These are the ill-gotten gains of crimes, such as the property taken from a home during a burglary.

Instrumentalities of crime:  These are the tools of the criminal that make committing a crime possible, such as burglary tools.

Most types of physical evidence can also be seized pursuant to a warrant.  Hairs, fibers, fingerprints, and such fall into this category.  There are, however, limits that the courts will not let law enforcement pass.  Such things as administering drugs to make a suspect throw up swallowed evidence have “shocked the court” and are thus prohibited.

Exceptions to the Warrant Requirement

The general rule is that a police officer needs a warrant to conduct a search for criminal evidence.  To issue such a warrant, a magistrate (judge) must determine that the evidence known to the officer is trustworthy and amounts to probable cause.  There are, however, many exceptions to the general rule. The following are a few well-known examples of exceptions to the general warrant requirement.  In other words, the court has established that police officers may conduct warrantless searches under certain limited circumstances.

“Special Needs” Searches.  Officers do not need any special evidence (PC) to justify a search in certain contexts, such as ports of entry into the United States from any other country (this includes all international airports).  Airline passengers are subject to suspicionless searches as well.

Some states allow the use of vehicle checkpoints to apprehend drunk drivers, but not every state allows this type of warrantless search even though it is allowable according the United States Constitution.

Stop and Frisk.  Brief questions and pat-down searches (also known as a stop-and-frisk) for weapons are permitted based on the reasonable suspicion of a police officer (Terry v. Ohio, 1968).  Note that reasonable suspicion is a lesser evidentiary standard than probable cause.  There are some limits, such as an anonymous tip being insufficient justification for a stop-and-frisk (Florida v. J. L., 2000). Note that the Supreme Court has recognized a substantial difference between a Stop and an Arrest.  A stop is a brief interference with someone’s liberty that can be measured in mere minutes.  Think of a “traffic stop.”

The officer may only detain you long enough to issue a warning, issue a citation, and so forth.  Prolonged investigations are not warranted. An arrest, on the other hand, is a prolonged detention, usually resulting in the suspect being taken to jail and processed into the criminal justice system.  Stops require a lesser evidentiary standard than do arrests because the impingement on the suspect’s liberty is much less.

Terry v. Ohio

“The crux of this case, however, is not the propriety of Officer McFadden’s taking steps to investigate petitioner’s suspicious behavior, but rather, whether there was justification for McFadden’s invasion of Terry’s personal security by searching him for weapons in the course of that investigation.  We are now concerned with more than the governmental interest in investigating crime; in addition, there is the more immediate interest of the police officer in taking steps to assure himself that the person with whom he is dealing is not armed with a weapon that could unexpectedly and fatally be used against him.  Certainly it would be unreasonable to require that police officers take unnecessary risks in the performance of their duties. American criminals have a long tradition of armed violence, and every year in this country many law enforcement officers are killed in the line of duty, and thousands more are wounded. Virtually all of these deaths and a substantial portion of the injuries are inflicted with guns and knives.  … In view of these facts, we cannot blind ourselves to the need for law enforcement officers to protect themselves and other prospective victims of violence in situations where they may lack probable cause for an arrest. When an officer is justified in believing that the individual whose suspicious behavior he is investigating at close range is armed and presently dangerous to the officer or to others, it would appear to be clearly unreasonable to deny the officer the power to take necessary measures to determine whether the person is in fact carrying a weapon and to neutralize the threat of physical harm.”

Search Incident to an Arrest.  Police can search people and areas in the immediate vicinity for weapons when a lawful arrest is made (Chimel v. California, 1969).

Exigent circumstances.  Officers might find themselves in the middle of an urgent situation where they must act swiftly and do not have time to request a warrant from the court.  Exigent circumstances will usually exist when it is believed that someone might be in grave danger.

Consent.  A citizen may waive his or her constitutional rights and allow police to search.  Police officers do not have to inform citizens of their right to decline a request to search under Federal Constitutional law (United States v. Drayton, 2002), but they do under the law of some states, such as Arkansas.  Police officers do not need a search warrant when suspects waive their Fourth Amendment rights.

Plain View Doctrine.  An object in plain view (out in the open) with a criminal nature that is readily apparent, may be seized by an officer without a warrant.  This type of ‘search’ is not considered a search for Fourth Amendment purposes (Coolidge v. New Hampshire, 1971).  In other words, police officers may lawfully seize evidence items that are visible to them when they are in a location that they are lawfully permitted to be.

In Horton v. California, (1990) the Court has held that a plain view doctrine seizure has three elements:

  1. The officer must already be lawfully present in an area protected by the Fourth Amendment
  2. the evidence item must be in plain view
  3. the officer must immediately recognize the item as evidence or contraband without making further intrusion

This third element means that the scope of the search cannot be expanded in the slightest way, or the Fourth Amendment will be violated.     

Automobile Searches.  Automobiles differ from homes in that they are mobile, and people generally have a lesser expectation of privacy in them.  The Court has ruled that automobiles (and containers within them) may be searched if probable cause exists, but without a warrant.

Carroll v. United States

“We have made a somewhat extended reference to these statutes to show that the guaranty of freedom from unreasonable searches and seizures by the Fourth Amendment has been construed, practically since the beginning of the government, as recognizing a necessary difference between a search of a store, dwelling house, or other structure in respect of which a proper official warrant readily may be obtained and a search of a ship, motor boat, wagon, or automobile for contraband goods, where it is not practicable to secure a warrant, because the vehicle can be quickly moved out of the locality or jurisdiction in which the warrant must be sought.”

Open Fields.  As a federal rule, open fields—undeveloped land outside the scope of the home and curtilage—is subject to search without constituting a ‘search’ for Fourth Amendment purposes.  Some states, However (e.g., MS), have restricted this rule.

The Exclusionary Rule

If evidence used in a criminal trial is obtained illegally (in violation of a person’s Fourth Amendment rights) it cannot be used in court.  In addition, according to the Fruits of the Poisoned Tree doctrine, any evidence stemming from the initial illegally obtained evidence is also excluded.  The rule was established by the courts as it applies to federal law enforcement in Weeks v. United States (1914).  It was not applied to local and state law enforcement until much later when the court decided Mapp v. Ohio (1961).

Mapp v. Ohio

“…The Court concluded that it was therefore obliged to hold, although it chose the narrower ground on which to do so, that all evidence obtained by an unconstitutional search and seizure was inadmissible in a federal court regardless of its source.  Today we once again examine Wolf’s constitutional documentation of the right to privacy free from unreasonable state intrusion, and, after its dozen years on our books, are led by it to close the only courtroom door remaining open to evidence secured by official lawlessness in flagrant abuse of that basic right, reserved to all persons as a specific guarantee against that very same unlawful conduct.  We hold that all evidence obtained by searches and seizures in violation of the Constitution is, by that same authority, inadmissible in a state court.”

Police Use of Force

In Tennessee v. Garner (1985), the court ruled that police may not lawfully use deadly force to apprehend an unarmed, nonviolent fleeing felon.  The underlying constitutional logic of this decisions was that doing so constituted an unreasonable seizure of the person under the Fourth Amendment.  Recall that the Fourth Amendment does not protect us from searches and seizures in general, only unreasonable ones.

Tennessee v. Garner

“The use of deadly force to prevent the escape of all felony suspects, whatever the circumstances, is constitutionally unreasonable.  It is not better that all felony suspects die than that they escape. Where the suspect poses no immediate threat to the officer and no threat to others, the harm resulting from failing to apprehend him does not justify the use of deadly force to do so.  It is no doubt unfortunate when a suspect who is in sight escapes, but the fact that the police arrive a little late or are a little slower afoot does not always justify killing the suspect. A police officer may not seize an unarmed, nondangerous suspect by shooting him dead.  The Tennessee statute is unconstitutional insofar as it authorizes the use of deadly force against such fleeing suspects.”

Key Terms

References and Further Reading


Modification History

File Created:  08/15/2018

Last Modified:  08/15/2018

[ Back | Content | Next]

This work is licensed under an Open Educational Resource-Quality Master Source (OER-QMS) License.

Open Education Resource--Quality Master Source License

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.