Section 3.2: The Fourth Amendment

Fundamentals of Policing by Adam J. McKee

“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.”

What Does the Fourth Amendment Do?

The Fourth Amendment is a crucial part of the United States Constitution. It’s all about protecting our privacy from the government. Imagine you have a secret diary. You wouldn’t want just anyone to read it, right? The Fourth Amendment helps make sure the government can’t just search your things or take them without a good reason. This includes your home, your backpack, your phone – pretty much anything you consider private.

Searches and Seizures: What’s Allowed?

When the police or other government agents want to search your stuff or arrest you, they have to follow rules set by the Fourth Amendment. If they don’t, the evidence they find might not be allowed in court. This makes sure that your privacy is respected and that the police act fairly.

More Than Just Property

Originally, the Fourth Amendment was thought to just protect physical things – like your house or your car. But in a big court case in 1967, Katz v. United States, everything changed. The court said it’s not just about your stuff; it’s about your privacy. This was a big shift! Now, whether it’s old-school letters or the latest smartphone, the main question is, “Do you expect it to be private?”

A Focus on Privacy

After the Katz case, the idea of privacy became key. Let’s say the police want to use a new gadget to see inside your house. The court would ask if you expected your house to be a private space. If the answer is yes, then they need a really good reason (like a warrant from a judge) to use that gadget.

Why Your Home is Super Important

Your home is like your personal fortress. The courts understand that you expect privacy there more than anywhere else. So, if someone wants to search your home, the Fourth Amendment makes sure they have a strong reason to do so.

🔍 Reflect

How do you feel about the idea of privacy in your own home? Can you think of any situations where it might be okay for the government to search someone’s home?


When Can Someone Be Arrested Without a Warrant?

Back in the day, if someone caused a big disturbance (like a “breach of the peace”) or committed a serious crime (a felony), they could be arrested right then and there, no warrant needed. This old rule still influences how things are done today. For example, if a police officer has good reason (called “probable cause”) to think you’ve committed a crime, they can arrest you in a public place without a warrant. But, if they want to arrest you at home, they usually need a warrant.

The Importance of a Warrant

A warrant is like a permission slip from a judge. It tells the police they have the okay to arrest someone. When an officer has a warrant, it’s like having a shield – it protects them legally. They don’t always need the warrant in their hand; just knowing there’s one out there is often enough.

Special Cases: Exigent Circumstances

Sometimes, there are urgent situations where waiting for a warrant might cause more harm. These are called “exigent circumstances.” In cases like these, the police can act without a warrant to make sure everyone stays safe.

The Fourth Amendment and Arrests

The Fourth Amendment doesn’t just cover searches; it also applies when someone is arrested (“seized”). This means that even if you’re just being held by the police and not formally arrested, your rights under the Fourth Amendment still matter.

How the Supreme Court Changed Things

For a long time, the Supreme Court didn’t really get involved in arrest cases. They used to think that even if you were grabbed by the police unfairly, you still had to go to court. But, things changed. Now, the courts look closely at how and why someone was arrested. If the police get a confession or some other evidence in a way that’s not fair, the courts might not let that evidence be used.

Bench Warrants: A Different Kind

A bench warrant is special. It’s issued by a judge when someone doesn’t follow court orders, like not showing up for a hearing. It’s a call to all police officers to arrest that person wherever they find them.

🔍 Reflect

How do you think the requirement for a warrant affects police work? Do you believe there are situations where officers should be able to act without one?

Probable Cause

What is Probable Cause?

Probable cause is like a puzzle piece in understanding our rights under the Fourth Amendment, but it’s a bit tricky because the Amendment doesn’t clearly define it. Think of it as more than just a guess, but less than being 100% sure, like in a criminal trial. It’s a standard set by judges over time, based on different cases.

How Do Courts Determine Probable Cause?

In a famous case, Draper v. United States (1959), the court gave us a clearer idea. They said it’s about having reasonable grounds to believe that a crime is happening. It’s like if you’re a detective in a mystery novel: you need enough clues that would make a careful and smart person think, “Yep, something illegal is going on here.”

Looking at the Big Picture

Courts use what’s called a “totality of the circumstances” test. This means they don’t just focus on one single piece of evidence. They look at everything – all the facts, all the details – to see the full story. It’s like putting together a jigsaw puzzle; you need all the pieces to see the whole picture.

The Role of the “Reasonable Man”

This concept is used a lot in court. It’s about what an average, sensible person would think in the same situation. But here’s the catch: it’s a bit subjective. What a police officer thinks is probable cause might not match what a judge thinks later. That’s why officers are often advised to get a warrant if they can. It’s like getting a second opinion to make sure they’re on the right track.

Trustworthiness of Information

When it comes to confidential informants, the courts exercise more caution. These informants are often involved in the criminal world themselves, and their motivations or honesty might be questionable. That’s why the courts look for additional evidence to support what an informant says. This process is known as corroboration.

Corroboration is about finding extra pieces of evidence that align with the informant’s story. It’s like putting together a puzzle where you need several pieces to see the whole picture. For instance, if an informant says a drug deal happens at a specific location, the police might look for additional signs like unusual activity or surveillance footage that supports this claim.

Evaluating the Informant’s Reliability

In addition to corroboration, the informant’s past reliability plays a crucial role. If they have a history of providing accurate information, their current information may be deemed more credible. It’s similar to trusting a friend who has always given you good advice in the past.

🔍 Reflect

Think about a time when you had to decide if something was true based on different pieces of information. How did you weigh the reliability of each piece? How does this relate to how the courts view probable cause?

Understanding Warrants and How They Work

Applying for a Warrant: The Basics

When someone, like a police officer, needs a warrant, they have to convince a judge that there’s good reason (probable cause) for it. This is like telling a story where every detail matters. The officer writes down all the important facts in a document called an affidavit. This is their promise that what they’re saying is true and it helps the judge decide if there’s enough reason to issue the warrant.

The Importance of Probable Cause in Warrants

Just like with searching a house or a car, when the police want to arrest someone, they need to show probable cause to get an arrest warrant. Remember, arresting someone is a big deal because it’s like the government is taking away their freedom. That’s why the Fourth Amendment’s rules about searches and seizures apply to arrest warrants too.

Neutral Judges: The Gatekeepers of Fairness

For a warrant to be legit, it has to come from a judge who’s neutral. Think of the judge as a referee in a sports game. They’re not cheering for one side or the other; they just want to make sure everything’s fair. The judge looks at the evidence and decides if it’s convincing enough to believe that the person might have done something illegal.

Why Judges, Not Police, Issue Warrants

It’s not that we think police officers are dishonest, but they’re really focused on catching people who break the law. Sometimes, they might be a bit too eager. Having a judge in the process is like having a second set of eyes to make sure everything’s fair and by the book.

The Particularity Requirement: Being Specific

The Fourth Amendment says that a warrant needs to be very specific. It should be crystal clear who is being searched or arrested, or which place is being searched. This is like when you’re giving someone directions; you wouldn’t just say “Go to the city.” You’d say, “Go to 123 Maple Street, the blue house with the red door.” That’s how specific a warrant needs to be.

🔍 Reflect

Why do you think it’s important for warrants to be specific? Can you think of any situations where being vague could cause problems?

Understanding What Can Be Seized by Police

The Three Main Categories of Seizable Items

When the police have a warrant, there are generally three types of things they’re allowed to take:

  1. Contraband: This includes items that are illegal to have in the first place. Think of things like drugs, unauthorized weapons, or explosives. It’s like having something you’re not supposed to have at all, like fireworks in a place where they’re banned.
  2. Fruits of Crime: Imagine someone steals a TV from a house. That TV is a “fruit of the crime” because it was gained illegally. It’s the stuff that criminals get by breaking the law.
  3. Instrumentalities of Crime: These are the tools used to commit a crime. For example, if someone uses special tools to break into cars, those tools are instrumentalities. It’s like the gear a thief uses to do their job.

Seizing Physical Evidence

Besides these three categories, police can also seize physical evidence that helps prove a crime happened. This can be things like hair, fiber from clothes, or fingerprints. It’s like collecting clues at a crime scene.

Limits on What Can Be Seized

However, there are boundaries. The police can’t do just anything to get evidence. For instance, they can’t force someone to take drugs to get them to cough up evidence they might have swallowed. The courts have rules against actions that are too extreme or shocking. It’s about balancing the need to solve crimes with respecting people’s rights and dignity.

🔍 Reflect

Why do you think it’s important to have limits on what can be seized? How do you balance the need to solve crimes with respecting individual rights?

Exceptions to the Need for a Warrant

When Do Police Not Need a Warrant?

Usually, police officers need a warrant to search for evidence. But there are some special cases where they can search without one. These are exceptions to the general rule that a warrant is necessary.

“Special Needs” Searches

In some situations, like at airports or border checkpoints, officers can search without specific evidence (probable cause). Airline passengers, for example, go through searches without any suspicion.

Stop and Frisk: Terry Stops

A police officer can stop someone and do a quick pat-down search if they have a reasonable suspicion that the person might be dangerous. This is different from an arrest; it’s more like a brief check for safety. The Supreme Court in Terry v. Ohio (1968) said this is okay because police officers need to protect themselves and others. They don’t need full probable cause, just a good reason (reasonable suspicion) to think someone might be carrying a weapon.

Search Incident to an Arrest

When someone is lawfully arrested, the police can search them and the area close by. This is to make sure there are no weapons that could be used against the officers.

Exigent Circumstances: Emergency Situations

Sometimes, officers find themselves in emergencies where they can’t wait to get a warrant. Like if they think someone is in immediate danger, they can act fast without a warrant.

Consent Searches

If a person agrees to let the police search, then the officers don’t need a warrant. This is called giving consent. But, the police don’t always have to tell you that you can say no to the search.

Plain View Doctrine

If a police officer is somewhere legally and sees something illegal in plain sight, they can seize it without a warrant. They just can’t go looking around more than what’s already visible to them.

Automobile Searches

Cars are different from houses because they can move quickly. The law says that if the police have good reason to think there’s evidence in a car, they can search it without a warrant.

Open Fields

Generally, undeveloped land that’s not part of someone’s yard (like open fields) can be searched without it being considered a Fourth Amendment search. But, some states have their own rules about this.

🔍 Reflect

Why do you think there are exceptions to the warrant requirement? How do these exceptions balance the need for public safety with individual rights?

The Exclusionary Rule: Keeping Out Illegal Evidence

What is the Exclusionary Rule?

The Exclusionary Rule is a key part of our legal system. It says that if evidence is found in a way that breaks someone’s Fourth Amendment rights (like an illegal search), it can’t be used in court. This rule is like a big red stop sign telling the police and the courts that they can’t use evidence that was obtained the wrong way.

Fruits of the Poisonous Tree Doctrine

This doctrine is like the Exclusionary Rule’s big brother. It says that not only is the illegally obtained evidence off-limits, but so is any other evidence that comes from that first piece of illegal evidence. Imagine if someone found a key illegally and that key opened a box with more evidence. None of that evidence can be used because the key was found illegally.

The Rule’s History

The Exclusionary Rule first came into play with a case called Weeks v. United States in 1914. Back then, it was just for federal law enforcement. It wasn’t until 1961, in a case called Mapp v. Ohio, that the rule was applied to local and state law enforcement too.

Mapp v. Ohio: A Turning Point

Mapp v. Ohio was a huge deal. The Supreme Court said that evidence found through unconstitutional searches and seizures couldn’t be used in state courts. This was a big step in making sure everyone’s rights are respected, no matter where they are in the United States.

🔍 Reflect

Why do you think the Exclusionary Rule and the Fruits of the Poisonous Tree doctrine are important in our legal system? How do they help ensure that justice is fair?

Use of Force: The Tennessee v. Garner Case

When Can Police Use Deadly Force?

In a landmark decision, Tennessee v. Garner (1985), the Supreme Court set clear limits on when police can use deadly force. The court said that police can’t use deadly force to stop someone who’s running away, if they’re unarmed and not dangerous. It’s like saying that the police can’t use extreme measures just because someone is trying to get away, especially if they’re not a threat.

The Fourth Amendment and Reasonable Force

This ruling is all about the Fourth Amendment, which protects us from unreasonable searches and seizures. Using deadly force on someone who’s not a threat or violent doesn’t fit the bill of being “reasonable.” It’s like the law saying there are certain lines you just can’t cross, even in police work.

Key Points from Tennessee v. Garner

The court made it clear that:

  • It’s not okay to use deadly force against every person suspected of a felony.
  • The police can’t justify using deadly force just because a suspect might get away.
  • It’s not constitutional to shoot an unarmed, non-dangerous person just because they’re fleeing.

The Importance of This Ruling

This case was a big deal because it set a standard for police officers all over the country. It’s about balancing the need for law enforcement to do their job with the rights and safety of individuals. It sends a message that while catching suspects is important, it’s not more important than preserving life, especially when the suspect isn’t a threat.

🔍 Reflect

How do you think this ruling impacts the way police officers make decisions in high-pressure situations? Why is it important to have clear rules about the use of force?


The Fourth Amendment of the United States Constitution is a vital component that safeguards individual privacy against unwarranted government intrusion. It ensures that people’s homes, personal belongings, and even their phones are protected from searches and seizures unless there’s a solid reason. This amendment has evolved over time, particularly highlighted in the landmark case of Katz v. United States (1967), where the focus shifted from protecting physical property to ensuring privacy. This change underscores the importance of the home as a private sanctuary, with courts upholding the necessity of a warrant for most home searches.

Arrest procedures are also governed by the Fourth Amendment. Historically, arrests without warrants were permissible under specific circumstances, like when a serious crime was witnessed. Nowadays, police need ‘probable cause’ to arrest someone without a warrant in public, but a warrant is typically required for home arrests. There are exceptions, however, such as urgent situations (exigent circumstances) where waiting for a warrant could be harmful. The necessity for a warrant underscores the importance of judicial neutrality in ensuring fair and lawful police actions.

Probable cause is a central concept in the Fourth Amendment but isn’t explicitly defined within it. It’s understood as more than a hunch but less than absolute certainty. Courts use a ‘totality of the circumstances’ approach to assess it, considering all available information. Confidential informants’ information needs corroboration, and their reliability is also crucial.

In terms of what can be seized, police can take contraband, fruits of crime, and instrumentalities of crime with a warrant. However, there are limits to what can be seized, emphasizing a balance between solving crimes and respecting individual rights.

There are several exceptions to the warrant requirement, including “special needs” searches at borders and airports, ‘Terry stops’ (stop-and-frisk), searches incident to arrest, exigent circumstances, consented searches, the plain view doctrine, automobile searches, and open fields doctrine. These exceptions balance public safety needs with individual rights.

The Exclusionary Rule plays a significant role in upholding the Fourth Amendment. Established in Weeks v. United States (1914) and extended to state law enforcement in Mapp v. Ohio (1961), it prevents illegally obtained evidence and its derivatives (Fruits of the Poisonous Tree doctrine) from being used in court.

Finally, the use of force by police is strictly regulated. Tennessee v. Garner (1985) set boundaries, ruling that deadly force cannot be used against unarmed, non-dangerous fleeing suspects. This decision emphasizes the need for reasonable force in policing, aligning with the Fourth Amendment’s stance against unreasonable actions. This ruling significantly impacts police decision-making in high-pressure situations, stressing the importance of clear, enforceable rules regarding the use of force.

Key Terms

References and Further Reading


Modification History

File Created:  08/15/2018

Last Modified:  12/13/2023

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

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