Illegal Search and Seizure and Probable Cause: What Are Your 4th Amendment Rights?

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.

One of the most confusing and controversial amendments in the Bill of Rights is also one of the most commonly reviewed in the Supreme Court. The Fourth Amendment regards illegal search and seizure, and basically says that law enforcement needs a reason to search you.

But we see time and time again how this is not straightforward at all, especially that part where it says “unreasonable.” We’ve all found that to be an ambiguous and, from a lawyer’s perspective, moldable term. For the past 15 years, and certainly more so since the revelations about the NSA, the most important issue to many Americans has been privacy. Intrusion on such has been blatant and horrifying on occasion, as law enforcement sometimes abuses their power and further blurs the line between suspicion and overreach.

What Constitutes Reasonable Suspicion?

Most of the time, reasonable suspicion arises during a traffic stop when the officer believes a crime may be afoot. However, that officer cannot pull you over for a broken taillight and then arbitrarily search your car. The officer must have stopped you believing a crime is being committed, and this includes DUI suspicion. But what exactly is “reasonable suspicion?” What protocol does law enforcement have to follow for this to apply?

Physical evidence is not required for an officer to harbor reasonable suspicion. An officer can say, “it smells like marijuana in the car,” and that’s all they need to justify a search. This is true everywhere except Massachusetts, which ruled two years ago that smell alone did not justify the search of a car, whether it was burnt or unburnt. The “smell “ excuse has been used countless times by police, and even cost one motorist over $63,000 in a despicable ruling by the U.S. Eighth Circuit Court of Appeals.

This is the thing; reasonable suspicion is such an ambiguous term that an officer can say pretty much anything to justify it. There are many resources out there that can tell you what law enforcement is allowed to do if they have reasonable suspicion, but none that tell you what exactly could give an officer reasonable suspicion in the first place. It is not clearly defined. This is not the same with probable cause.

What Constitutes Probable Cause?

Whereas reasonable suspicion is a bit general, probable cause has much more clearly defined parameters. This is mainly due to it actually being specifically cited in the Fourth Amendment.

Probable Cause Definition: Probable cause is a reasonable belief that a person has committed or will commit a crime. A police officer must have sufficient knowledge of facts to warrant a belief that a suspect is committing a crime and it may not be based on merely suspicion. The belief must be based on factual evidence. An officer MAY have probable cause in the following situations:

  • Observation – If he is walking up to your car and sees a gun in the back seat, or drugs, that officer can pretty much do whatever he wants.
  • Circumstantial evidence – such as swerving – implies something occurred, like a DUI, but doesn’t 100 percent prove it. This still gives probable cause for a car search, or in this situation, a breathalyzer.
  • Expertise – The training which allows officers to identify movements or gestures as potentially criminal. We’ve seen how wrong this can be in the past, however.
  • Information – statements or testimony by witnesses or victims can be enough to justify probable cause.
  • Sensory – If the officer smells alcohol on your breath or marijuana in the car, this gives probable cause for a search.
  • Consent – I.E. you agree to the search.

You may be asking yourself, “Doesn’t law enforcement need a warrant to conduct a search?” In many circumstances, this is true. For example, the Email Privacy Act was unanimously passed by the House recently, which means that a warrant, and not just a subpoena, is required to search through your email, including those stored on any cloud services. However, there are still plenty of situations for which an officer does not need a warrant to conduct a search.

When Is a Search Warrant Not Necessary?

It is a commonly held belief that police has to have a search warrant to look through your car or home. Apart from the probable cause described above, there are numerous situations where a warrant is unnecessary.

  • Automobile Exception – Reasonable suspicion still applies, but an officer is allowed to search your car without a warrant because of the need for immediate action.
  • Emergency Exception – In direct relation to immediate action, law enforcement can conduct a warrantless search if getting a warrant will take too long and jeopardize public safety or will result in the destruction of evidence.
  • Plain View – This goes back to the observation which justifies probable cause. If an officer sees drugs or weapons of any kind, that gives them reasonable suspicion to search the rest of the car or house.
  • Stop and Frisk – Operating under reasonable suspicion, an officer can perform this on anyone he suspects of criminal activity.

There is one more situation in which a warrant is not necessary, and that is consent. However, as with everything else in search and seizure, this is not black and white.

How Does Consent Relate to Search?

Another commonly held misconception is that consenting to a search will make the whole process easier for you, which simply isn’t true. It actually opens you up to a host of other problems, especially if you sign any paperwork without a lawyer present; suddenly your wiggle room, if you need any, shrinks significantly. There are varying levels of consent that can be applied to many different situations.

Implied consent usually arises in impaired driving cases. If you drive while impaired, you are giving implied consent because you are using public roads, and are subject to search of your car or yourself. The argument that this revokes due process has been denied by the courts, and functions under the theory that driving on public roads is a privilege, not a right.

Express consent comes in the form of written or verbal communication to law enforcement. This essentially waves Fourth Amendment rights, as an officer can open a box or container within your car if they have reasonable suspicion that weapons or drugs may be present. There are limits you can put on this search. For example, you can consent to a search of your car, but exclude the trunk as being part of that search.

There are numerous outlying factors, quid pro quo’s and exceptions which could affect the validity of consent. It’s a topic that has been studied and debated under numerous circumstances, and has established specific nuance to search and seizure.

When Has the Fourth Amendment Appeared in Supreme Court Cases?

Almost too often to count. More than a dozen cases have come before the high bench in the past 15 years alone, with many more having come in past decades. Out of all of these, there are three which had a profound effect on the public’s understanding of the Fourth Amendment, as well as law enforcement’s application of it.

Terry v. Ohio(1968) is perhaps one of the most important search cases decided by the Supreme Court, purely because of the precedent it set. Three men were pacing outside of a jewelry store, and a plainclothes officer suspected a robbery was about to take place. He stopped them, identified himself and frisked them, finding weapons. In an 8-1 majority, the Court upheld the conviction and the submission of the weapons as evidence, based on the reasonable suspicion – and not just a hunch – of the officer that the men might be about to commit a crime.

Safford USD v. Redding(2009) was a hot-button case because it involved school administrators and two students. Redding, a 13-year-old girl, was strip-searched by two officials based on a tip from another student that she had unauthorized ibuprofen on her, which was against school policy. Her mother sued the district, claiming her Fourth Amendment rights protecting her against unreasonable search were violated. In another 8-1 majority, the Court ruled that Redding’s rights were indeed violated, particularly because the “drugs” they were looking for did not pose a threat to the school.

In relation to this, the ever-increasing use of technology has led to much debate about how searches of phones should be handled, especially in school. The argument is that a student’s cell phone is their, or more often their parent’s, personal property, even if it’s confiscated by the school for inappropriate use. It has been ruled that a cell phone cannot be searched without a warrant.

Fernandez v. California(2009) is another case which was important towards interpreting the law, because it took into account a new situation. Fernandez had robbed another man named Lopez, and police were able to track down Fernandez to his apartment. Upon knocking, a woman named Rojas answered. When police asked her permission to search the apartment, Fernandez came forward and refused entry. Upon seeing him, the officers arrested Fernandez for the robbery, and then returned to ask Rojas permission to search a second time, to which she consented. They found drugs and weapons. All of this is notable for one reason: the search was conducted without a warrant.

In a 6-3 majority, the Court ruled that the warrantless search did not violate the Fourth Amendment. Normally a search would be unconstitutional when two tenants of an apartment are present and one denies permission. However, when one of those tenants is arrested and removed in conjunction with a crime, searching the place without a warrant is justified under reasonable suspicion.

There has been a recent firestorm over border security, the center of which has occurred in Arizona. The cause of this is a hotly debated bill that had a direct effect on illegal search law, and had many proponents on either side of the argument.

How Does Illegal Search Relate to Arizona SB 1070?

This controversial bill deemed it legal for police to stop and search someone if the officer held a reasonable suspicion that that person was an illegal immigrant. It gave them carte blanche in that it did not matter the situation; someone walking down the street minding their own business could be under just as much scrutiny as someone pulled over for egregious speeding. This became immediately problematic, particularly because of its racist overtones, as it’s hard to imagine police stopping a white man to ask for their immigration papers.

Upon being signed into law in April of 2010, it was almost immediately brought to the Supreme Court. The provisions of the bill said that it was a misdemeanor to not have your immigration papers on you at all times, seek work without authorization, required officers to verify citizenship and allowed for warrantless arrests. In Arizona v. United States(2012), all but one (verifying citizenship) of the provisions was struck down as unconstitutional in a 5-3 vote.

All of the aforementioned delegations give a lot of protection to the citizen, but there is one provision that might seem contradictory to some, and affords a lot of protection to law enforcement.

What Is Mistake of Fact?

Mistake of fact refers to when an officer perceives you are breaking a law, when in actuality you are not. The officer has not misinterpreted the law, he has only misinterpreted what he saw. A lot of times this applies to a traffic stop. For example, an officer sees you take a drink from a bottle, and pulls you over on suspicion of drinking and driving. Upon approaching your window, he sees that it was just a soda bottle. Any ticket issued in this situation would be rendered invalid, however the stop itself was made within reason, and is therefore not a violation of any of your rights.

This is different from mistake of law, which refers to an officer detaining someone based on an improper understanding of law. However, this does not mean that anything uncovered during this detaining is inadmissible. This was discussed in Heien v. North Carolina(2014) in which Heien was pulled over for a broken taillight. He consented to a search of his car, and officers discovered cocaine. Heien was booked on drug trafficking charges. However, under North Carolina law, only one working taillight is necessary. So he argued that since he was not breaking the law that the stop was unnecessary, and therefore any evidence obtained during the stop was inadmissible. In an 8-1 decision, the Court ruled that the drugs were in fact admissible, because the mistake about the law was “reasonable.”
It’s quite possible that you’ve found one or two contradictory anecdotes throughout this article. Such is the consequence of trying to interpret the Fourth Amendment. Since so much of this relates to traffic stops, one thing to remember is that, if you happen to have prior arrests or convictions, they have no bearing on the situation at hand. The cop does not have “reasonable suspicion” or “probable cause” based on past grievances; those things have to apply to the current situation.

(Update, June 21st: the Supreme Court has just ruled in Utah v. Strieff that if you have so little as an unpaid traffic ticket, then the police are justified in searching you or your car, and whatever they find is admissible as evidence. Justice Sonia Sotomayor wrote a scathing dissent of the decision, summarizing it as the whittling down of Fourth Amendment rights.)

A couple of questions to ask yourself if an officer requests to search your car: what was the officer’s reason for pulling me over, and did I do something or did he see something to give him reasonable suspicion? You have the right to refuse to consent to search under almost all circumstances, and the most important thing to remember is not to sign anything without an attorney present.

B. Clausen

A graduate of the University of Kansas, Brian Clausen is the U.S. news reporter for Dopplr. Before joining the team, he created digital content for large companies.


  • Is probable cause so loosely defined that it allows for slander and perjury by law enforcement? I would hate to believe that yet with my legally aquired belongings being held as evidence and with me being stopped regularly by a roving band of thugs that are good for planting evidence, I can only watch in amazement at how the residents of this city tolerate these actions.
    It is no doubt,my responsibility to appear for court whenever I am served a citation . However, with my short term memory issues, I rely upon those documents for the designated dates and times for my apearrance. Due to Bullies with Badges and their so-called searches, I have lost paperwork not only for court, but registration, insurance even my ID. My friend and assistant labelled a prostitute and my previous vehicle trashed to the point of being unrecognizable.
    Of course there is no fear of retribution by the police but as I go through this railroaded dance of legalized law breaking I refuse to accept these “overzealous,greedy, unworthy of the name pigs” as the standard in law enforcement. To go to the extremes they do to create a “case” is not law enforcement. It is merely a response to ones need for justification of existence or in more advanced stages of the mental stigma associated with the French Emporer/ Dictator Napoleon…it’s the street name for a syndrome that causes an over abussive attitude when in position of some authority… Short Dick Syndrome.

  • I was stopped by an officer because he said it looks like you cant afford the bike i was riding so he lied in. Court said he saw me stealing bike parts but it was all a lie. Then he confiscated my bike and phone because i won’t unlock phone and case was dismissed After 7 MONTHS of. Incarceration.BIKE was RETURN ed do i have a case

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