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Lesson 6: When Does a Law Enforcement Officer Have Probable Cause to Conduct a Search or Make an Arrest?

The Fourth Amendment tells us that any warrants issued to search or seize (arrest someone) must be based upon “probable cause”. Law enforcement officers must go to a judge (called a “magistrate” in this context) in order to obtain a warrant based upon probable cause. When they do, they must convince the judge that there is a reasonable basis to believe that the person they want to arrest has committed a crime, or that the place that they will search contains evidence of a crime.

If it is shown that a warrant was not based on enough evidence to meet the probable cause standard, then the warrant is invalid and any evidence obtained using it will have to be suppressed (excluded, prevented from being used in the case). Recall how the defense attorney for T.L.O. believed that the school had no probable cause to search her. They would have been correct if she had not been a minor.

The evidence that is the basis for a warrant can come from one of several sources, including victims or witnesses, an accumulation of facts that together suggest that a crime was committed, or even observations made by the police officer(s).

For example, someone can call the police and inform them that a drug dealer makes a sale every day at a certain time and location. If the informant provides sufficient detail about witnessing these drug deals including the time and place and a detailed description of the dealer, and if the police have been able to verify who the informant is and that they are reliable, the police will be able to obtain an arrest warrant from a magistrate.

When they apply for a warrant, police officers are presumed (assumed) to be giving reliable information but they still must provide an affidavit (a legally binding pledge that they are telling the truth) when asking for a warrant. The magistrate may also consider the officer’s years of training and experience when they evaluate the application for a warrant.

There are six exceptions to the warrant requirement, which we will describe below. Even if a search is conducted without a warrant it must always be based upon probable cause. This ensures that the search, consistent with the Fourth Amendment, is not “unreasonable.” This Reasonableness Requirement demands that the government weighs its duty to protect our privacy against the duty to provide for the public’s safety. The reasonableness requirement is defined as:

circumstances that would cause a reasonable person to believe that entry (or other relevant prompt action) was necessary to prevent physical harm to the officers or other persons, the destruction of relevant evidence, the escape of the suspect, or some other consequence improperly frustrating legitimate law enforcement efforts.

Most searches are actually conducted without a warrant so it is important to understand the legal basis for these searches.

Warrantless Searches Based on Probable Cause

Consent Search
If an individual gives a police officer consent to search their belongings, home, or person, the officer may do so without obtaining a warrant. Also, consent can be granted by family or housemates living in the same residence as the person whose room or belongings the police want to search, if that person is not at home. If a child is suspected of a crime, a parent can give their consent for a police officer to search their child’s bedroom or belongings. A child may be able to give valid consent to a search if they are old enough to understand what a search involves and if they can provide access to the part(s) of the home listed in the warrant. If no parent is present and the child is the only person home, they may be able to give their full consent. However, they cannot be forced to do this. They should not consent to a search unless the officer shows them a warrant and they fully understand it.

The consent exception is based on the assumption that when a person consents to a search they are willingly giving up their expectation of privacy. However, the validity of someone’s consent as a justification for a warrantless search depends upon their age, mental capacity, and their understanding of the implications of their consent. Consent is invalid if an individual has been coerced, intimidated or bribed to offer their consent, or if an officer asserts their official status and claims they have a right to conduct a search.

When you give consent to a search, you may limit your consent to a specific search, for example, by restricting the search to just one room in a house. In that case it is important to record that limited consent in writing and ask that the officer sign it. Once you give your consent to a search it cannot be revoked. If you consent to a vehicle search, you cannot call it off in the middle of the search.

Search Incident to Arrest
The search incident to arrest exception is intended to ensure that a person being arrested will not use a weapon against an arresting officer and that no evidence of the crime for which they are being arrested is destroyed. These purposes are requirements, so the search must be based upon these. When you are arrested, police may search anything in the area of your “immediate control”, meaning anything that is within your arm’s reach.

If a police officer pats you down looking for a weapon and finds your wallet, they are not entitled to examine its contents unless they have probable cause to believe that it contains a weapon. They may take it as evidence if they have reason to believe it may contain evidence but it must be examined later when they have a warrant to search it because nothing within it is going to disappear as they take it back to the station. If an officer is arresting someone for selling drugs, they can search them and their bags for drugs and seize them as evidence if they find any.

Normally, while the police may search the outside of your cell phone or underneath the case, they may not search the phone itself without a warrant to specifically search it. However, if police suspect that there is evidence of a crime on the phone that may disappear, like a message, they may turn the phone off, place it in a bag that protects against radio waves, or disable its automatic encryption lock to prevent the data from being lost. If the officer believes that there is an exigent circumstance (pressing or urgent), like if they must look in the phone to learn about the location of a bomb, or of a missing child, they are allowed to search the phone incident to an arrest.

Respecting the old English adage “a man’s home is his castle”, you are given added protections to the arrest exception in your home. In the state of Massachusetts, in most cases, if you have not consented to a search and are not presented with a specific search warrant, a police officer entering your home to make an arrest may only seize evidence that is in “plain view” and is obviously incriminating.

Vehicle Search (Sometimes referred to as an Automobile Search)
When a person is pulled over in their vehicle and they are believed to have committed a crime, their vehicle may be searched without a warrant if the officer has probable cause based on a reasonable belief that either evidence may be destroyed or that there is a threat to officer safety. Probable cause for a search, for example, can be if the driver of the vehicle was swerving between lanes on the highway. In this situation, the officer can search the vehicle for open containers of alcohol or illegal drugs, since it is illegal to consume alcohol or illegal drugs in a vehicle. The reason an officer does not have to first obtain a warrant for a vehicle search when they have probable cause to believe a crime was committed is because, unlike a home, the vehicle can be driven away, and when this happens there is a high likelihood that evidence will not be recovered.

Plain View Search
This exception allows a police officer to seize contraband (anything that it is illegal to have), or evidence of a crime, that is in the plain sight of the officer. The “plain view doctrine” exists so that a law enforcement officer does not have to risk that the evidence of a crime will be disposed of while they go to a magistrate to obtain a warrant. The plain view exception applies even when you have not been arrested. So, if an officer sees an open alcohol container or illegal drugs through a car window as they are issuing a traffic violation, they are allowed to take these as evidence.

However, the officer is not permitted just to stroll up to a parked car in a private driveway and peer in the windows, nor may they drive up to someone’s home and search it from the yard unless they have a search warrant or are making an arrest. They are allowed to peer through windows while they are standing in a public area.

Activity 1
Questions about Probable Cause and the Exceptions to It

The Reasonableness Requirement must be met to establish probable cause for the government to conduct a search. What are the four criteria that are reasonable justifications for a search?

a.
b.
c.
d.

If an officer wants to conduct a search what must they provide to a magistrate? Do you think this affects whether officers search people in a racially equitable way? Why, or why not?

Must someone consent to a search if they have not been shown a warrant?

Under what circumstances can the consent that someone has given to a search be seen as invalid (and therefore the evidence be suppressed)?

a.
b.
c.
d.
e.

In the absence of a warrant, when a law enforcement officer arrests you, what conditions allow them to carry out a search of you and the area within your reach?

a.
b.

If you refuse to provide your name, address, date and place of birth and nationality after you have been told by the police why they have stopped to question you, you could be arrested in MA for not answering them. If they arrest you, they can pat-search you to check for weapons. Are they allowed to look in a bag that you are carrying for illegal drugs? Explain.

If a police officer pulls your vehicle over because you are driving with an expired license plate, can they search your car? Why or why not? (Driving with an expired license plate is a misdemeanor in MA and you will receive a citation but not be arrested.)

If an officer is directing traffic and as you drive by, they notice an open can of beer in your car, and stop and arrest you, can they search the car for more contraband? Why or why not?

Searches Based Upon a Reasonable Suspicion

“Stop-and-Frisk” or Terry Stop
In the stop-and-frisk exception to the warrant requirement, the officer needs only a reasonable suspicion as opposed to probable cause to conduct the search. The justification for this is that the officer believes that the suspicious behavior that they observe may be threatening violence. So a frisk cannot be a full search; it is only to look for a weapon by patting down the outer layers of someone’s clothing. The officer is not allowed to look for illegal drugs or evidence for any other crime. If, however, you are frisked in Massachusetts, and a concealed weapon is found and you lack a permit for the weapon, then the officer can search you for other evidence.

As you have just heard, the stop-and-frisk exception comes from the Supreme Court case, Terry v. Ohio 392 U.S 1 (1968). In this case, a police officer saw three people walking back and forth past a store many times while looking in its window. The officer suspected that these individuals were planning to rob the store. He approached them, patted one of them down and found a gun in the individual’s coat-pocket. He then patted down the other two people and found more firearms. At trial, the defense attempted to get the weapons excluded as evidence. But the court decided that when the individuals engaged in behavior that reasonably led the police officer to be suspicious that they were planning an armed robbery, the officer was justified in doing a quick, noninvasive search, described in the court decision as “plain touch” of an individual, analogous to a plain view search. As a result of this case, pat-downs like those in this stop-and-frisk encounter with the police, are also called Terry Stops.

Exigent Circumstances
Exigent circumstances occur when a “reasonable” officer determines that a situation is an emergency and there is no time to obtain a warrant. “Reasonable” in this context means that the officer’s decision that this was an “emergency” is consistent with what most officers would have concluded under the same circumstances. In her majority opinion in Lange v. California, in 2021, Justice Elena Kagan said that the Court (SCOTUS) has previously found that “exigencies may exist when an officer must act to prevent imminent injury, the destruction of evidence, or a suspect’s escape.”

In a Massachusetts case in 2019, Commonwealth v. Jose Arias, a woman called the police to an apartment building because she saw “two Spanish guys” enter a building and heard one of them loading a gun. There had been “home invasions” in the neighborhood and the Lawrence Police Department had received a tip that “a crew from New York” was responsible. The police staked out the front and rear of the building. After receiving more information about the layout of the building, they reconnected with the 911 caller who then told them that she saw three men enter apartment 5A. The police went there and when no one responded to a knock, they broke in. They found no one in the apartment but they saw narcotics, many plastic bags and a scale. After leaving the apartment, they searched the building looking for armed men or victims. They found three men hiding who they arrested and charged.

The defendant who owned the apartment filed a motion to suppress the evidence on the basis of an illegal search. The case was appealed to the Massachusetts Supreme Judicial Court. It evaluated whether the circumstances met two requirements:
“First, the police need an objectively reasonable basis to believe that an emergency exists at the time of entry. Second, once police enter the apartment, they must be reasonable under the circumstances and not exceed the scope of the search. Commonwealth v. Entwistle, 463 Mass. 205, 213 (2012).”

“The Supreme Judicial Court held that based on the facts in this case, the emergency aid exception did not apply because an emergency did not exist and police lacked an objectively reasonable basis to believe that a home invasion was in progress, or that some type of safety risk was posed to potential victims inside the apartment.”

Therefore the arrests were unreasonable.

Another exception to the requirement for a warrant based on probable cause occurs in schools:
“School officials need not obtain a warrant before searching a student who is under their authority; rather, a search of a student need only be reasonable under all the circumstances.” From: New Jersey v. TLO, 469 U.S. 325 (1985).

Concerns about the Racial Equity of Stop-and-Frisks and Vehicle Searches
Recently there has been a lot of discussion about the racial inequity (lack of fairness) of both “stop-and-frisk” and vehicle searches. Here is some data on this.

The ACLU reviewed data on stop-and-frisk searches in Washington D.C. and determined that not only are 25% more people of color stopped and searched compared to their proportion in the population, but only 0.8% of all people searched by the police had a weapon of any kind. The ACLU also conducted a study on stop-and-frisk racial disparities in New York City and found that “between 2014 and 2017, Black and Latino males between the ages of 14 and 24 represented only five percent of the city’s population but accounted for 38 percent of reported stops.” Young Black and Latino males were more likely to be frisked than White males and a smaller proportion of those frisks found weapons compared to the frisks of White males.

A national study was conducted in 2020 analyzing reports of 100 million traffic stops carried out by 21 state patrol agencies and 35 municipal police departments over almost a decade comparing the frequency of stops of people of color before compared to after sunset. The study found that Black drivers were 30% more likely to be stopped during daylight than after sunset. The study also revealed that Black and Hispanic drivers were searched on the basis of less evidence than White drivers.

In response to the recent high profile killings of Black motorists by police during stops for traffic violations, some cities have decided to eliminate police stops for minor traffic offenses like burned out-brake or headlights, rear view mirror decorations or lack of emissions inspection stickers. These changes have often come after many local citizens called, wrote and met with their local mayors, city councilors and police chiefs. (These cities include Pittsburgh, Philadelphia, Seattle, Berkeley, Lansing, and Brooklyn Center. The State of Virginia also changed this legislation.)

Questions About Terry v. Ohio (Related to the podcast by Cedric Hopkins Esq.

Please consider the following questions as a group. Please assign a different person to read the group answer for each question to the class when you are finished.

After listening to the SCOTUS decision in Terry v. Ohio did anything change in your view about whether what the officer did was legal? Please explain why or why not. If different people in the group have different answers, write these down to discuss with the class.

Based upon the decision, explain why an officer is allowed to conduct a Terry Stop.

Exactly what is an officer allowed to do in a Terry Stop?

What was the evidence that the police officer had that gave them reasonable suspicion to believe that John Terry, Richard Chilton and Carl Katz should be searched?

Assignment
Please read the vocabulary for Lesson 7 on pages 38-40. Please explain below how accurate data collection about crime and law enforcement enables us to better protect the Constitutional rights of minority groups in the United States?

On pages 41-46 you will find a publication, “Know Your Rights” from the Electronic Frontier Foundation. It is optional reading but recommended.

Supplementary Handout
“Know Your Rights”
Electronic Frontier Foundation, last updated October 2014.
By Hanni Fakhoury and Dia Kayyali
https://www.eff.org/issues/know-your-rights#37

Your computer, phone, and other digital devices hold vast amounts of personal information about you and your family. This sensitive data is worth protecting from prying eyes, including those of the government.

The Fourth Amendment to the U.S. Constitution protects you from unreasonable government searches and seizures, and this protection extends to your computer and portable devices. But how does this work in the real world? What should you do if the police or other law enforcement officers show up at your door and want to search your computer?

EFF has designed this guide to help you understand your rights if officers try to search the data stored on your computer or portable electronic device, or seize it for further examination somewhere else. Keep in mind that the Fourth Amendment is the minimum standard, and your specific state may have stronger protections.

Because anything you say can be used against you in a criminal or civil case, before speaking to any law enforcement official, you should consult with an attorney. Remember‚ generally the fact that you assert your rights cannot legally be used against you in court. You can always state: "I do not want to talk to you or answer any questions without my attorney present." If they continue to ask you questions after that point, you can say: “Please don’t ask me any further questions until my attorney is present.” And if the police violate your rights and conduct an illegal search, often the evidence they obtain as a result of that search can’t be used against you.

We’ve organized this guide into three sections:

Overview: When can the police search my devices?

If you consent to a search, the police don’t need a warrant.

The most frequent way police are able to search is by asking you for permission. If you say “yes” and consent to the search, then police don’t need a warrant. You can limit the scope of that consent and even revoke or take it back after the officers begin searching, but by then it may be too late.1 That’s why it’s better not consent to a search--police may drop the matter. If not, then they will generally need to get a search warrant to search.

Law enforcement may show up at your door. Apart from a few exceptions, police need a warrant to enter your home.

The police can’t simply enter your home to search it or any electronic device inside, like a laptop or cell phone, without a warrant.
When the police knock on your door, you do not have to let them in unless they have in their possession and show you a valid search warrant. The safest thing to do is step outside and shut the door behind you. They may or may not indicate right away why they are there. If they have a warrant, ask to see it. If they offer to simply “interview” you, it is better to decline to speak until your attorney can be present. You can do this by telling the officer: “I do not want to talk to you. I do not consent to a search. I want to speak to my attorney.”

There are two major exceptions to the warrant requirement. First, if you consent to a search, then the police can search within the scope of your consent. That’s why it is usually better to not consent to a search.

Second, if police have probable cause to believe there is incriminating evidence in the house or on an electronic device that is under immediate threat of destruction, they can immediately search it without a warrant.

Be aware that the police can ask your roommate/guest/spouse/partner for access to your computer if they don’t have a warrant.
The rules around who can consent to a search are fuzzy. The key is who has control over an item. Anyone can consent to a search as long as the officers reasonably believe the third person has control over the thing to be searched.4 However, the police cannot search if one person with control (for example a spouse) consents, but another individual (the other spouse) with control explicitly refuses.5 It's unclear, however, whether this rule applies to items like a hard drive placed into someone else’s computer.6 And even where two people have control over an item or place, police can remove the non-consenting person and return to get the other's consent to search.

You may want to share this know your rights guide with everyone in your home and ask them not to consent to a search by law enforcement.

Even if you're arrested, police can only search your phone under limited circumstances.

After a person has been arrested, the police generally may search the items on her person and in her pockets, as well as anything within her immediate control, automatically and without a warrant. But the Supreme Court has ruled that police cannot search the data on a cell phone under this warrant exception.8 Police can, however, search the physical aspects of the phone (like removing the phone from its case or removing the battery) and in situations where they actually believe evidence on the phone is likely to be immediately destroyed, police can search the cell phone without a warrant.

Police can search your computer or portable devices at the border without a warrant.

Fourth Amendment protection is not as strong at the border as it is in your home or office. This means that law enforcement can inspect your computer or electronic equipment, even if they have no reason to suspect there is anything illegal on it.

An international airport, even if many miles from the actual border, is considered the functional equivalent of a border.

However, border officials in Alaska, Arizona, California, Guam, Hawaii, Idaho, Montana, Northern Mariana Islands, Oregon and Washington can only confiscate an electronic device and conduct a more thorough “forensic” examination of it if they have reasonable suspicion you’ve engaged in criminal behavior.

(My addition: In a 2019 decision on a case involving a forensic search of the phone at a border entry point in Massachusetts, the judge determined that border agents must have “reasonable suspicion” that a device contains digital contraband before searching or seizing the device. However, there have been no similar decisions, so unfortunately if you are within 100 miles of a border or the ocean, Customs and Border Patrol or ICE can search your devices. This means that if you are driving in Maine within 100 miles of the border, you can be stopped and have your phone or other electronic device searched. For recommendations by the American Bar Association on how to handle an order or request to unlock your device, including a cell phone, please see: https://www.americanbar.org/groups/business_law/publications/blt/2020/04/border-searches/.

In October of 2021 Senators Ron Wyden and Rand Paul introduced the Protecting Data at the Border Act to stop the government from forcing Americans to face indiscriminate and suspicionless searches of their phones, laptops and other digital devices at borders and entry points or within 100 miles of a border. Representative Ted Lieu, D-Calif., introduced a companion bill in the House of Representatives.”)

The police have a warrant. Now what?

Ask to see the warrant.

A warrant is a document signed by a judge giving the police permission to either arrest you or search your property and take certain items from that property. You have the right to see the warrant and should check to make sure it is valid.
A warrant should contain:

The correct name of the person arrested or the correct address of the specific place to be searched;
A list of the items that can be seized or taken by the police;
The judge’s signature;
A deadline for when the arrest or search must take place

The police must take the warrant with them when executing it and give you a copy of it.

They must also knock and announce their entry before they try to forcefully enter your home,14 and must serve the warrant during the day in most circumstances.

The warrant limits what the police can do.

The purpose of the warrant is to give the judge, not the police, the discretion to decide what places can be searched and which items can be taken.16 That’s why a warrant is supposed to state exactly what the police can search and seize.

However, if the warrant authorizes the police to search for evidence of a particular crime, and such evidence is likely to be found on your computer, some courts have allowed the police to search the computer without a warrant.

And remember, if you consent to a search, it doesn’t matter if the police have a warrant; any search is permissible as long as the search is consistent with the scope of your consent.

Although the warrant limits what the police can look for, if they see something illegal while executing a warrant they can take it.
While the police are searching your home, if they observe something in "plain view" that is suspicious or incriminating, they may take it for further examination and can rely on their observation to later get a search warrant.

For example, if police see an open laptop with something obviously illegal on the screen, they could seize that laptop.

If the police want to search your computer, it doesn’t matter whether you’re the subject of their investigation.

It typically doesn’t matter whether the police are investigating you or think there is evidence they want to use against someone else located on your computer. If they have a warrant, if you consent to the search, or they think there is something incriminating on your computer that may be immediately destroyed, the police can search it. But remember, regardless of whether you’re the subject of an investigation, you can always seek the assistance of the lawyer.

You do not have to assist law enforcement when they are conducting their search.

You do not have to help the police conduct the search. But you should not physically interfere with them, obstruct the search or try to destroy evidence, since that can lead to your arrest. This is true even if the police don’t have a warrant and you do not consent to the search, but the police insist on searching anyway. In that instance, do not interfere but write down the names and badge numbers of the officers and immediately call a lawyer.

You do not have to answer questions while law enforcement is searching.

You do not have to answer any questions. In fact, because anything you say can be used against you and other individuals, it is best to say nothing at all other than “I do not want to talk to you. I do not consent to a search. I want to speak to my attorney.” However, if you do decide to answer questions, be sure to tell the truth. In many contexts, it is a crime to lie to a police officer and you may find yourself in more trouble for lying to law enforcement than for whatever it was on your computer they wanted.

The police can’t get into my computer. Now what?

The police can take your computer with them and search it somewhere else.
As long as the police have a warrant, they can seize the computer and take it somewhere else to search it more thoroughly. As part of that inspection, the police may make a copy of media or other files stored on your computer.

You do not have to hand over your encryption keys or passwords to law enforcement.

The Fifth Amendment protects you from being forced to give the government self-incriminating testimony. Courts have generally accepted that telling the government a password or encryption key is “testimony.” A police officer cannot force or threaten you into giving up your password or unlocking your electronic devices. However, a judge or a grand jury may be able to force you to decrypt your devices in some circumstances. Because this is a legally complicated issue, if you find yourself in a situation where the police, a judge or grand jury are demanding you turn over encryption keys or passwords, you should let EFF know right away and seek legal help. (My addition: Currently, the police do not need you to supply a password to access your cell phone because many police departments have access to specialized password cracking tools like Cellebrite or GrayKey. We will discuss this in a later lesson.)

You may be able to get your computer back if it is taken and searched.

If your computer was illegally taken, then you can file a motion with the court to have it returned.

If the police believe that evidence of a crime has been found on your computer (such as possessing “digital contraband” like pirated music and movies, or digital images of child pornography), the police can keep the computer as evidence. They may also attempt to keep the computer permanently, a legal process known as forfeiture, but you can challenge forfeiture in court.

There is less protection against a search at a place of employment.

Generally, you have some Fourth Amendment protection in your office or workspace.

This means the police need a warrant to search your office and work computer unless one of the exceptions described above apply. But the extent of Fourth Amendment protection depends on the physical details of your work environment, as well as any employer policies. For example, the police will have difficulty justifying a warrantless search of a private office with doors and a lock and a private computer that you have exclusive access to. On the other hand, if you share a computer with other co-workers, you will have a weaker expectation of privacy in that computer, and thus less Fourth Amendment protection.25 However, be aware that your employer can consent to a police request to search an office or workspace in your absence.26 Plus, if you work for a public entity or government agency, no warrant is required to search your computer or office as long as the search is for a non-investigative, work-related matter.

Want to learn more about how to protect yourself from unreasonable government searches and surveillance on your computer or portable electronic devices?

EFF’s newly relaunched Surveillance Self-Defense (SSD) is a guide to defending yourself and your friends from digital surveillance by using encryption tools and developing appropriate privacy and security practices.
EFF’s recently updated Cell Phone Guide for U.S. Protestors explains your rights, and how best to protect the data on your phone, at protests.
Source for all of the above: https://www.eff.org/issues/know-your-rights#37

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