SEARCH
What are the two independent ways a government action can qualify as a Fourth Amendment search?
(1) Physical trespass to obtain information (trespass test); or (2) invasion of a reasonable expectation of privacy (Katz test).
What is the constitutional threshold for a full custodial arrest?
Probable cause that the person committed, is committing, or is about to commit a crime.
What is the general Fourth Amendment rule regarding searches or seizures conducted without probable cause?
A search or seizure conducted without probable cause is generally unreasonable.
What are the two types of warrants used in Fourth Amendment analysis?
Arrest warrants and search warrants.
What is required for a Terry stop?
Reasonable suspicion—specific, objective facts that suggest criminal activity is afoot. It’s less than probable cause but more than a hunch.
What are the three requirements of the plain view doctrine?
Lawful vantage point, lawful right of access, and it must be immediately apparent that the item is contraband or evidence.
What is the basic rule for the consent exception to the Fourth Amendment?
Consent allows a warrantless search without probable cause as long as the consent is voluntary.
What is the first question you must ask before applying the search-incident-to-arrest exception?
Whether the arrest itself was lawful. SILA applies only if the arrest is valid.
What two conditions trigger the automobile exception under Carroll?
The vehicle must be readily mobile, and officers must have probable cause to believe it contains contraband or other seizable evidence.
What are the main categories of exigent circumstances that permit warrantless entry or search?
Hot pursuit, danger to officers or others, risk of evidence destruction, and other emergencies where obtaining a warrant is impractical.
What must a defendant show to have standing to suppress evidence under the Fourth Amendment?
They must show a personal violation—that their own person, house, papers, or effects were searched or seized, meaning they had a legitimate expectation of privacy in the place searched (Rakas).
Why do roving border patrol stops require reasonable suspicion, but fixed checkpoints do not?
Roving stops give officers broad discretion and surprise motorists, creating higher privacy risks, so reasonable suspicion is required. Fixed checkpoints (Martinez-Fuerte) are predictable, standardized, and minimally intrusive, so individualized suspicion isn’t needed.
What features of cell-site location information (CSLI) make long-term acquisition of it a search?
It is automatically generated, highly precise, deeply revealing of private life, and provides a comprehensive record of a person’s movements over an extended period. OUR PHONES ARE OUR LIVES. WE TAKE THEM EVERYWHERE.
What justifies an investigative stop (Terry stop), and what must officers point to?
Specific, articulable facts giving reasonable suspicion that criminal activity is afoot
How do courts treat evidence that is lawful in itself when used to justify probable cause?
Hint: case of the black man carrying a lawful firearm
Lawful conduct cannot create probable cause unless it is accompanied by additional facts that make criminal activity reasonably likely; otherwise, innocent behavior cannot be transformed into suspicion.
When does an arrest at the doorway become a “constructive entry” that triggers Payton’s rule requiring a warrant to enter the home?
When police use coercion, commands, or show of authority that causes the suspect to leave the home or pulls the suspect into a public space; because the person did not voluntarily expose themselves to public arrest, Payton applies and officers cannot treat it as a lawful public arrest.
What are the basic levels of justification under the reasonableness clause for stop, frisk, and arrest?
A Terry stop needs reasonable suspicion of criminal activity; a Terry frisk needs reasonable suspicion the person is armed and dangerous; an arrest requires probable cause that a crime occurred.
Does the plain view doctrine allow officers to seize an item they were already hoping to find, or must the discovery be accidental(Inadvertent)?
It does not need to be accidental; Horton holds that inadvertence is not required.
"There’ s no reason to draw a distinction between an item found by accident and one that's anticipated. The interference w/ the individuals possessory interest is the same. This won’t turn specific warrants into general warrant’s b/c that interest is served by the warrant particularity rule"
How do courts decide whether consent was voluntary under Schneckloth?
Courts use the totality of the circumstances—looking at everything about the person (age, education, experience) and the encounter (tone, number of officers, setting). Knowing you can refuse helps, but the police don’t have to tell you that for consent to be valid.
What two areas may officers automatically search during a lawful arrest under Chimel?
The arrestee’s person and the immediate grabbing area from which the arrestee could access a weapon or destroy evidence.
Under the automobile exception, when may officers search containers found in a car?
When probable cause to search the vehicle extends to the container, and the container is large enough to hold the evidence they are looking for.
What level of suspicion is required for officers to act under the community-caretaking or emergency-aid exception?
They need only reasonable grounds to believe someone needs immediate assistance—not probable cause—and the action must be objectively focused on safety, not investigation.
Why did the passengers in Rakas lack standing to challenge the search of the glove compartment?
Because passengers normally have no privacy interest in areas they don’t control—like the glove box or under the seat. They can challenge their own seizure, but not the search of compartments belonging to the driver or car owner.
What type of item does the automobile exception not apply to, even when the item is found inside a vehicle?
Digital data on cell phones, because phones contain vast private information and require a warrant.
What doctrine explains why sharing information with another person (including an undercover agent or informant) eliminates Fourth Amendment protection for that information?
The False Friends Doctrine holds that when you voluntarily share information with another person — even if that person is secretly a government informant or undercover agent — you assume the risk they will disclose it to law enforcement.
Under the reasonable person test, when has a seizure occurred during a police encounter?
When a reasonable, innocent person would not feel free to decline the officer’s requests or end the encounter. (Mendenhall/Drayton framing)
When a court reviews whether probable cause existed for a police action, what perspective does the judge apply, and what factors about the officer can be considered?
The judge evaluates the officer’s conduct objectively from the standpoint of a “reasonable officer,” taking into account the officer’s training, experience, and familiarity with the particular area.
When may officers skip the knock-and-announce requirement before executing a search warrant?
When they have reasonable suspicion—based on specific facts, not a hunch—that knocking would be dangerous, futile, or risk destruction of evidence. (Richards)
Under U.S. v. Johnson, why can’t an officer seize a single bullet during a Terry frisk?
Because a bullet by itself is not inherently dangerous and does not make the person “armed and presently dangerous.” Terry permits a pat-down only for immediate safety risks, and a lone bullet does not justify expanding the frisk.
In Arizona v. Hicks, why did moving a stereo turntable violate the Fourth Amendment?
Because moving the item exposed concealed information not already in plain view, it made it a separate search requiring probable cause.
Why isn’t consent valid if officers claim they have a warrant, like in Bumper?
Because saying “we have a warrant” leaves the person with no real choice—refusal becomes meaningless. Any consent given after a false or misleading claim of legal authority is automatically invalid.
What determines the scope of the “grabbing area” under SILA?
Practical factors such as whether the arrestee is handcuffed, the ratio of officers to the arrestee, the arrestee’s size and mobility, and the physical layout of the space.
What rule did Chambers establish about searching a vehicle at the station instead of at the scene?
If probable cause existed at the stop, officers may conduct a warrantless automobile-exception search either immediately at the scene or shortly afterward at the station.
What did Caniglia v. Strom clarify about the “community caretaking” doctrine?
That while police may enter to provide emergency aid, there is no broad, free-standing community-caretaking exception for warrantless home entry unrelated to immediate safety concerns.
We understand that it may be a reason, but we have to protect the CRIB, it can't just be free-range!!!
What protection does Simmons give defendants who testify at a suppression hearing?
Their testimony to establish standing cannot be used against them at trial to prove guilt, preventing self-incrimination—but it may still be used for impeachment or lead to investigative consequences.
When may police use deadly force against a fleeing suspect under the Fourth Amendment?
Only when the suspect poses an immediate threat of serious harm to officers or others; fleeing alone is not enough. Garner
Under Katz, what two components must be shown to establish that a search occurred?
(1) The person exhibited a subjective expectation of privacy; and (2) the expectation is one society is prepared to recognize as reasonable.
What distinguishes the seizure of a person from the seizure of property under the Fourth Amendment?
A person is seized when their freedom of movement is restrained by force or authority; property is seized when the government meaningfully interferes with an individual’s possessory rights.
Why are “mere suspicions,” “gut feelings,” or reputational assertions insufficient to establish probable cause?
Because probable cause requires objective, reasonably trustworthy information—not bare conclusions or speculation—so the magistrate must be able to independently assess the facts rather than rely on unsubstantiated assertions.
When can police enter a suspect’s home to make an arrest, and how does the doorway rule affect whether the suspect is considered “in public” or “in the home”?
Police may enter a suspect’s home only with an arrest warrant (or exigent circumstances). However, a suspect standing in the open doorway is treated as being in public, so a warrantless arrest is permitted—but once the suspect retreats inside, Payton prohibits entry unless exigent circumstances such as hot pursuit apply.
How do courts treat high-crime areas and flight when assessing reasonable suspicion?
Being in a high-crime area alone is not enough, but unprovoked flight in such an area can establish reasonable suspicion under the totality of the circumstances (Wardlow). But flight cannot justify a stop if police created the confrontation by aggressively boxing someone in (Brown).
What is the difference between observing a serial number and moving an item to see a serial number under the plain view doctrine?
Observing a visible serial number is permissible with no seizure; moving the item to reveal hidden information is a search and requires probable cause.
When can one occupant give police consent to search a shared home?
Under Matlock, any co-occupant with “common authority”—joint access or control—can consent as long as the other occupant is not physically present to object. By sharing a space, you assume the risk the other person might allow police in.
What did Robinson establish about the scope of a search of the arrestee’s person?
A full search of the arrestee’s person—including containers on the body—is always reasonable after a lawful custodial arrest, regardless of additional probable cause.
When does the automobile exception apply to motor homes under Carney?
When the motor home is readily movable and located in a non-residential or public place, reflecting reduced privacy expectations similar to cars, not when it is set up as a residence (Which would look like being on a platform, or bricks instead of tires, located in a trailer yard).
How does Brigham City v. Stuart illustrate the emergency-aid form of exigent circumstances?
Officers may enter a home without a warrant when they reasonably believe someone inside faces imminent harm, based on objective observations like fighting or visible injury.
When police obtain evidence after an unconstitutional search or seizure, what does the Fruit of the Poisonous Tree doctrine require courts to decide, and what are the main ways the government can still get that evidence admitted?
Courts must decide whether the evidence was caused by the illegal search or seizure. If the evidence grew out of that illegality, it is normally excluded. But the government can still admit it if one of three exceptions applies:
Independent Source: Officers later obtained the same evidence from a completely lawful, untainted route—one not influenced or triggered by the illegal search.
Inevitable Discovery: Officers would have found the evidence anyway through routine, lawful procedures (e.g., ongoing search teams, inventory processes).
Attenuation: The connection between the illegal act and the evidence has become weak through Wong Sun Factors.
What standard governs all excessive-force claims during a seizure, and from whose perspective is it judged?
The objective reasonableness standard under the Fourth Amendment, evaluated from the perspective of a reasonable officer on the scene, not with hindsight. Graham
What two elements must the government satisfy to establish a search under the trespass theory?
(1) A physical intrusion on persons, houses, papers, or effects; and (2) the intrusion must be for the purpose of obtaining information.
What level of suspicion must officers have to justify a Terry frisk, and what is its scope?
Reasonable suspicion that the person is armed and dangerous; the search is limited to a pat-down of outer clothing for weapons only.
What principle does Draper illustrate about when an informant’s tip can establish probable cause?
When a tip gives very specific, predictive details that police later confirm, that confirmation shows the informant likely had real inside knowledge, which is enough to create probable cause.
What warrant is required when police want to arrest a suspect inside someone else’s home, and why?
Police need a search warrant for the third-party home because the arrest warrant protects only the suspect, not the privacy of the third party. Entering the third-party home requires separate judicial authorization identifying that the suspect is likely inside. (Steagald)
Why did the anonymous tip in Alabama v. White create reasonable suspicion even though it was weak?
Because the tip accurately predicted White’s future behavior, giving it reliability. Under the totality of the circumstances, predictive details suggested the caller had inside knowledge, which is enough for reasonable suspicion even if it wouldn’t meet probable cause.
What does “immediately apparent” mean in plain view analysis?
Officers must have probable cause that the item is contraband or evidence at the moment they see or feel it—reasonable suspicion is not enough.
What rule does Randolph create when one occupant objects and another consents?
A physically present occupant’s “no” overrides the other’s “yes.” If both are at the door and one says no, police cannot enter without a warrant unless an exigent circumstance exists.
Why does Riley hold that searching a cellphone’s digital contents is not permitted under SILA?
Because phones contain massive amounts of private information, and the SILA justifications (weapons and evidence destruction) do not apply to digital data. Officers may seize the phone but generally need a warrant to search it absent exigent circumstances.
Why did Coolidge and Collins limit the automobile exception for vehicles parked at a home?
Because the automobile exception does not override the heightened Fourth Amendment protection of the home and its curtilage; officers must obtain a warrant when the car is on private residential property and no exigency exists.
What justifies warrantless entry in situations involving potential destruction of evidence?
Specific, objective facts indicating that evidence is at immediate risk—such as sounds of movement suggesting destruction—create an exigency that allows officers to enter without waiting for a warrant.
If police illegally enter a building and see incriminating items but later obtain a warrant, what must they show for the evidence to be admissible under the Independent Source Doctrine?
They must show the later warrant-based search was genuinely independent of the illegal entry:
The decision to seek the warrant was not triggered or motivated by what officers saw during the unlawful entry.
No information from the illegal entry was presented to the judge or used to obtain the warrant.
If the warrant was based only on information gathered before the illegal search, the evidence is admissible (Murray).
What rules determine whether officers may bring a drug-sniffing dog to a particular location, and what rules determine whether the dog’s alert creates probable cause?
A dog’s presence violates the Fourth Amendment when officers bring it into an area they have no lawful access to—such as the home’s curtilage or a porch beyond the implied license—making the sniff itself an unlawful search. But if the dog is lawfully present, its alert generally creates probable cause so long as the dog is properly trained and certified, though defendants may still challenge reliability through evidence of false alerts, handler cueing, or poor testing.
When does using technology to obtain details about the inside of a home become a search under the Fourth Amendment?
When the device is not in general public use, it reveals information about the interior that could not otherwise be obtained without physical intrusion.
What four types of items may be seized consistent with the Fourth Amendment when probable cause exists?
Fruits: tangible things directly gained as a result of a crime
Instrumentalities: Tools used to commit a crime
Contraband: Illegal goods
Mere evidence: items that provide proof of a crime but weren’t used in it’s commision (ex :a shirt)
What are the two prongs of the Aguilar–Spinelli test for evaluating informant tips?
Basis of Knowledge: The informant must explain how they know the information (for example, saw it firsthand or heard the plan).
Veracity:This asks why the magistrate should trust the informant, and it has two parts:
Credibility: Shown when the informant has a good track record (e.g., past tips led to arrests or convictions).
Reliability: Shown when the circumstances make it unlikely the informant is lying, such as when the tip is against their own interest or self-incriminating.
Does a search warrant for a premises and a specific person allow officers to search everyone found on-site?
No. Officers need independent probable cause for each person; a warrant for the premises or named individual does not authorize frisking or searching other occupants. (Ybarra)
Why did the detention in Florida v. Royer exceed the limits of a Terry stop?
Because officers moved Royer from a public concourse to a private room, kept his ID and ticket, and searched his luggage without probable cause—turning the encounter into a de facto arrest.
What is the “plain touch” rule, and when does it allow seizure?
Under Minnesota v. Dickerson, officers may seize contraband felt during a lawful frisk only if its incriminating nature is immediately apparent by touch without manipulation.
How does Fernandez limit Randolph’s objection rule?
If the objecting occupant is legally removed—such as being arrested—then the remaining occupant’s consent becomes valid. Randolph stops applying once the objector is no longer present.
Under Birchfield, why may officers administer breath tests incident to DUI arrests but not blood tests?
Breath tests are minimally intrusive and involve low privacy interests, while blood tests pierce the skin, extract biological samples, and reveal significantly more information—requiring a warrant absent exigency.
Under Acevedo, when may officers open a specific container inside a vehicle without a warrant?
When they have probable cause that the container itself holds contraband or evidence; the automobile exception allows both searching the car for the container and opening the container once found.
Why did the Court uphold the warrantless entry in Warden v. Hayden under the “hot pursuit” doctrine?
Because officers were actively pursuing a fleeing suspect who had just entered the home, and it was reasonable to enter immediately to capture him and locate any weapons.
When officers execute a search warrant that later turns out to be unsupported by probable cause, why might the evidence still be admissible under the good-faith exception, and when does the exception NOT apply?
Evidence is admissible when officers reasonably relied on a warrant they believed was valid because exclusion would not deter misconduct—they followed the process in good faith (Leon).
But good faith does not apply if:
the officer lied or recklessly omitted facts in the affidavit;
the warrant was facially deficient (so lacking in probable cause that no reasonable officer would rely on it);
the judge was not neutral and detached; or
police conduct shows deliberate, reckless, or systemic negligence rather than ordinary mistakes.
The key question: Would a well-trained officer have known the warrant was defective?
When can officers conduct a protective sweep during an in-home arrest?
Officers may do a quick, limited sweep of spaces where a person could be hiding if they have specific, articulable facts suggesting danger. They may also automatically check areas immediately adjoining the arrest site from which an attack could be launched. The sweep must be brief, only for people—not evidence—and end once
When does aerial observation of a homeowner’s property constitute a search?
Only when the aircraft is in a vantage point not commonly used by the public, or when the surveillance is so intrusive (e.g., excessive noise, wind, repeated hovering, or revealing intimate details) that it defeats any reasonable expectation of privacy.
What case illustrated that physical force is considered a seizure even if the person does not stop or is not subdued?
When the officer applies physical force with the intent to restrain, even if the person escapes. (Torres v. Madrid)
bullets striking Torres constituted a seizure under the Fourth Amendment because the officers intended to restrain her, though the seizure lasted only as long as the force was applied.
How does the Illinois v. Gates totality-of-the-circumstances test modify the older Aguilar–Spinelli framework?
Gates retains basis of knowledge and veracity as factors but eliminates the rigid two-prong requirement; a deficiency in one can be compensated by strength in the other, so the magistrate makes a common-sense judgment whether there is a fair probability that evidence or contraband will be found.
How far does a search warrant extend when officers reasonably but mistakenly believe they are in the place described in the warrant?
The search is valid only until officers realize the mistake; once they know they are in the wrong location, they must stop. (Garrison)
What three factors does the Texas v. Brown balancing test evaluate when deciding whether a suspicionless checkpoint—like a sobriety checkpoint—is reasonable under the Fourth Amendment?
It weighs (1) the state’s interest—such as reducing drunk-driving accidents,
(2) the effectiveness of the checkpoint in serving that interest (a very low bar), and
(3) the level of intrusion on drivers, both objectively (brief, mild stop) and subjectively (fear or surprise).
When searching computer files, how does plain view apply?
Only files the officer is lawfully reviewing may fall under plain view; it cannot justify rummaging or opening files outside the authorized scope (Frasier).
What does the “apparent authority” rule allow officers to rely on?
Officers may enter if a reasonable officer would believe the consenting person had authority over the space—based on facts observed at the scene—even if it later turns out they didn't actually have authority.
Under Arizona v. Gant, when may officers search a vehicle incident to the arrest of a recent occupant?
Only when (1) the arrestee can still access the passenger compartment at the time of the search, or (2) it is reasonable to believe the vehicle contains evidence of the offense of arrest. Routine traffic offenses rarely satisfy prong 2.
What principle does Chadwick illustrate about searching luggage or personal containers not immediately associated with the arrestee?
Once officers have exclusive control of personal luggage outside the vehicle, and no exigency exists, a warrant is required to search it because containers carry greater privacy expectations than automobiles.
"EFFECTS"
When does the police-created exigency doctrine bar officers from relying on exigent circumstances to justify a warrantless entry?
Only when police create the exigency by violating or threatening to violate the Fourth Amendment; lawful conduct like knocking and announcing does not invalidate the exigency.
When does the attenuation doctrine allow evidence to be admitted even though it followed an illegal search or seizure?
Evidence is admissible when the causal link between the police misconduct and the evidence has become weak enough that excluding it would not meaningfully deter police behavior. Courts apply the Brown factors to decide this:
Time passed: More time between the illegal act and the evidence → weaker connection.
Intervening events: Something new and lawful occurs—like discovery of a valid arrest warrant (Strieff)—breaking the chain.
Purpose/flagrancy of misconduct: If police acted deliberately or in bad faith, attenuation is less likely; if the misconduct was minor or negligent, attenuation is more likely.
Why were sobriety checkpoints upheld in Michigan v. Sitz under the special needs doctrine?
Because the state’s interest in preventing drunk-driving deaths is strong, the checkpoints are effective enough (low bar), and the intrusion is brief and standardized. The balancing test favored the government since the purpose is roadway safety—not general crime detection.
Which case held that squeezing a bus passenger’s bag is a search, and why?
Bond v. United States — because physical manipulation reveals concealed information not exposed to the public.
When does a show of authority become a seizure under the Fourth Amendment?
Only when the person actually submits to the officer’s command; no submission means no seizure. (Hodari D.)
When is a defendant entitled to a Franks hearing to challenge a warrant affidavit?
Only when they make a substantial preliminary showing that the affiant knowingly, intentionally, or recklessly included a material false statement; the rule applies only to the affiant because only the affiant is under oath.
Under the Fourth Amendment’s reasonableness requirement, how do courts evaluate police actions taken to prevent the destruction of evidence—both when entering a home after knocking and announcing, and when temporarily restraining a person while waiting for a warrant?
Courts ask whether the police acted reasonably under the circumstances by considering the nature of the evidence and the risk of its destruction. A short wait before forced entry may be justified when the evidence is easily disposable (as in drug cases), and a temporary, limited restraint on a suspect may be reasonable if it is minimally intrusive, time-limited, and used to preserve evidence while officers obtain a warrant.
Banks and McArthur
How do courts decide whether the length of a detention turns a Terry stop into a de facto arrest, and why did the 16-hour airport detention of the woman who swallowed a balloon still count as a valid Terry stop?
Length alone doesn’t decide whether a stop becomes an arrest. Under Sharpe, the question is whether officers acted diligently to confirm or dispel their suspicions and whether the detention lasted no longer than necessary for that purpose. The 16-hour airport detention was upheld as a Terry stop because officers continuously worked to verify whether she had swallowed contraband, so the delay was tied to the investigation—not police delay or unnecessary intrusion.
How do courts distinguish between lawful tactile discovery and unlawful manipulation under the plain-touch/plain-view framework?
If the incriminating nature is obvious from initial lawful contact, seizure is allowed; but if the officer manipulates, squeezes, or probes the object to confirm suspicion, that is an unlawful search (Dickerson; Hatcher illustrates minimal handling that merely confirms what is already apparent).
What assumption-of-risk principle explains why third-party consent works at all?
When you share a space with someone who has joint access or control, you take the risk they may allow others—including the police—inside. The Fourth Amendment treats that shared control as permission for either occupant to consent unless a present co-occupant objects.
How does Whren interact with SILA in pretextual traffic stops?
If officers have objective probable cause for any traffic violation, the stop is valid regardless of motive. Once a lawful custodial arrest follows, SILA permits a full search of the arrestee and, under Gant, possibly the vehicle—officer motives do not invalidate objectively reasonable action.
This conflicts with Driving while black.
How do courts distinguish between the automatic search authority for items “immediately associated with the person” and the limits on searching larger containers under the automobile exception?
Items on the arrestee’s person (like the cigarette pack in Robinson) may always be searched incident to arrest, but larger containers or luggage—once secured and not on the arrestee—require a warrant unless the automobile exception applies based on probable cause tied to the car, not merely to the person.
How does the exigent-circumstances doctrine limit the scope of a warrantless search once officers lawfully enter, and what happens when the emergency ends?
Officers may search only areas reasonably related to the specific exigency—such as places where a suspect, weapon, or threatened person could be found—and the authority to search ends the moment the emergency ends.
How have Hudson, Herring, and Davis significantly narrowed the exclusionary rule, and what common principle ties these cases together?
Hudson v. Michigan: Violating knock-and-announce does not trigger exclusion because officers already had a valid warrant, so discovery was inevitable and exclusion wouldn’t deter misconduct.
Herring v. U.S.: Evidence isn’t excluded when an arrest is made based on a negligent clerical error by police. Only deliberate, reckless, or systemic errors justify suppression.
Davis v. U.S.: No exclusion when officers rely on binding appellate precedent later overturned; they were following the law as it existed, so there’s no deterrent value in exclusion.
Common principle: The exclusionary rule applies only when exclusion will meaningfully deter sufficiently culpable police misconduct. If deterrence is minimal, courts will admit the evidence despite a violation.
When does the “special needs” exception allow suspicionless seizures to be reasonable under the Fourth Amendment?
When the government action serves non-criminal objectives—like safety, public welfare, or administrative needs—and not general crime control. Courts use a balancing test weighing (1) the government’s interest, (2) the program’s effectiveness, and (3) the level of intrusion on privacy.