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Warrantless searches of automobiles

The questions that follow explore whether the Fourth Amendment bars police from searching a car, its driver, or passengers without a search warrant, or restricts the scope of such a search (click on the chart on the right for an overview).

Some states have provided greater protections for criminal suspects under their constitutions and statutes, but the emphasis here is on settled federal principles resolved by the United States Supreme Court (which set the baseline in state litigation as well).

Lets begin with the initial encounter, which will typically fall within one of three categories. Police may make routine traffic stops with a show of authority (signaling the driver to pull over with lights or siren). Sometimes a traffic stop is made without individualized suspicion, as part of a roadblock or checkpoint. Other times police approach a car that is already stopped.


startroadblock or checkpoint

If the stop is at the border or its functional equivalent (i.e., an international airport), a search of the vehicle or the occupants is lawful without probable cause or reasonable suspicion. United States v. Ramsey, 431 U.S. 606, 616 (1977); Almeida-Sanchez v. United States, 413 U.S. 266 (1973).

Title 8 U.S.C. § 1357(a)(3) provides authority for fixed checkpoints designed to intercept illegal aliens ("immigration checkpoints"). Brief, suspicionless seizures of motorists at these checkpoints, or similar checkpoints to detect drunk drivers or to verify drivers' licenses and vehicle registrations are apparently permissible. See City of Indianapolis v. Edmond, 531 U.S. 32, 37-38 (2000). However, a suspicionless stop at a roadblock established to "uncover evidence of ordinary criminal wrongdoing" is impermissible. Id. at 42.

Decisions may not be based on the "unconstrained exercise of discretion" or "unbridled discretion of police officers." Delaware v. Prouse, 440 U.S. 648, 663 (1979). There needs to be an element of randomness (e.g., every tenth car).

The roadblock or checkpoint was:


startno stop

If the vehicle is already stopped and unoccupied, there is normally no seizure that would trigger Fourth Amendment concerns. This may be true as well for stopped but occupied vehicles because "a person is 'seized' only when, by means of physical force or a show of authority, his freedom of movement is restrained." United States v. Mendenhall, 446 U.S. 544, 553 (1980). Id. at 554. Simply requesting identification, without more, is not detention. Id.

Note also that suspicionless stops of individuals may be lawful where the circumstances are so compelling that the warrantless search is objectively reasonable under the Fourth Amendment. See Brigham City, Utah v. Stuart, 547 U.S. 398, 399 (2006) (emergency aid doctrine).

Police may not enter a home or its curtilage to look at a vehicle without a warrant unless a warrant exception applies. Collins v. Virginia, 584 U.S. ___ (2018).

Evidence was discovered during:


start ... inventory?

Even if probable cause does not exist, there might be authority to impound a vehicle for community caretaking purposes. Lawfully impounded vehicles may be inventoried for the purpose of protecting the owner's property while it is in police custody; protecting the police against claims of lost or stolen property; protecting the police from potential danger; or to determine whether a vehicle has been stolen and thereafter abandoned. South Dakota v. Opperman, 428 U.S. 364, 369 (1976).

The search may extend to closed containers. Police retain some discretion regarding what to open, "so long as that discretion is exercised according to standard criteria and on the basis of something other than suspicion of evidence of criminal activity." Colorado v. Bertine, 479 U.S. 367, 375 (1987). "A police officer may be allowed sufficient latitude to determine whether a particular container should or should not be opened in light of the nature of the search and characteristics of the container itself." Florida v. Wells, 495 U.S. 1, 4 (1990) (unlawful because police had no policy whatsoever with respect to the opening of closed containers).

The evidence was discovered and seized:


start ... inevitable discovery?

The stop or search was unlawful, so the evidence will be suppressed unless the government can justify the search under the independent source, inevitable discovery, or attenuation doctrines.

First, the independent source doctrine allows trial courts to admit evidence obtained in an unlawful search if officers independently acquired it from a separate, independent source. Second, the inevitable discovery doctrine allows for the admission of evidence that would have been discovered even without the unconstitutional source. Third, ..., is the attenuation doctrine: Evidence is admissible when the connection between unconstitutional police conduct and the evidence is remote or has been interrupted by some intervening circumstance, so that "the interest protected by the constitutional guarantee that has been violated would not be served by suppression of the evidence obtained."
Utah v. Strieff, 136 S.Ct. 2056, 2061 (2016) (emphasis added).


startvehicle stop

Traffic stops made with a show of authority are "seizures" under the Fourth Amendment that ordinarily must be supported by a reasonable suspicion of a crime or traffic violation. Delaware v. Prouse, 440 U.S. 648, 654 (1979). The stop may be lawful even if the officer makes a reasonable mistake of fact or law. Heien v. North Carolina, 135 S.Ct. 530 (2014). See also Kansas v. Glover, No. 18-556 (U.S. Apr. 6, 2020).

These stops may be lawful without a reasonable suspicion of a crime or traffic violation if made under the "emergency aid" doctrine, that is, the circumstances are so compelling that the warrantless search is objectively reasonable under the Fourth Amendment. See Brigham City, Utah v. Stuart, 547 U.S. 398, 399 (2006).

A traffic-violation stop or arrest is not rendered invalid by the fact that it was pretext for a search for evidence on another more serious charge. Arkansas v. Sullivan, 532 U.S. 769, 772 (2001).


start ... consent?

A lawfully stopped car can be searched if the officer asks for and receives a voluntary consent to the search. The consent need not be knowing and intelligent, i.e., the subject need not be advised of a right to refuse consent or be told of the consequences of such consent. See United States v. Drayton, 536 U.S. 194, 206-07 (2002).

The duration of the stop may last no longer than is necessary to effectuate its purpose. Authority for a seizure "ends when tasks tied to the traffic infraction are—or reasonably should have been—completed." Rodriguez v. United States, 135 S. Ct. 1609, 1614 (2015). This would invalidate a consent obtained after the duration of a stop was unlawfully extended.

The scope of a consent search is limited to what a "typical reasonable person have understood by the exchange between the officer and the suspect." Florida v. Jimeno, 500 U.S. 248, 251 (1991) (closed container).


start ... lawful stop

A police officer who has made a lawful traffic stop lawfully seizes the driver and all of the passengers for the duration of the stop. See Brendlin v. California, 551 U.S. 249, 255 (2007). During this period of time, the officer may discover evidence as part of plain view or smell observation from outside the vehicle, a records check, the sniffing of the outside of the vehicle by a trained narcotics detection dog, or during a patdown of the driver or passenger.

Evidence was discovered during:


start ... lawful stopfrisk

During the period of time required to make an inquiry into a vehicular violation, police with a reasonable suspicion that the driver or passenger is armed and dangerous may pat that person down (frisk) for weapons. Arizona v. Johnson, 555 U.S. 323, 327 (2009).

The evidence was seized during a frisk that was


start ... lawful stopcanine sniff

During the course of a legitimate traffic stop, police officers with no further suspicion of any illegal activity may nevertheless use a drug-detection dog to sniff the vehicle. Illinois v. Caballes, 543 U.S. 405 (2005). The police may not, however, extend the duration of a routine traffic stop beyond the time required to complete the normal administrative matters attendant to such a stop, not even for a de minimus period of time. Rodriguez v. United States, 135 S.Ct. 1609 (2015).

The canine narcotics alert occurred:


start ... lawful stopprobable cause?

Based on the officer's plain view or plain smell observations from outside the car, or information from other sources (e.g., the records check or a canine sniff), the officer:


start ... lawful stop ... probable causeincident to arrest?

Search of a person incident to arrest. A person arrested for a crime may be searched incident to the arrest, even if there is no concern about the loss of evidence, or that the suspect may be armed. United States v. Robinson, 414 U.S. 218, 236 (1973).

Search of the vehicle incident to arrest. "Police may search a vehicle incident to a recent occupant's arrest only if the arrestee is within reaching distance of the passenger compartment at the time of the search or it is reasonable to believe the vehicle contains evidence of the offense of arrest." Arizona v. Gant, 556 U.S. 332, 350 (2009).

The search is of the:


start ... probable causeincident to arrestclosed container?

A search incident to an arrest is limited to "personal property ... immediately associated with the person of the arrestee." United States v. Chadwick, 433 U.S. 1, 15 (1977) (can't open locked footlocker). Cf. United States v. Robinson, 414 U.S. 218, 236 (1973) (officer permitted to open cigarette package); Riley v. California, 134 S.Ct. 2473, 2485 (2014) (Robinson does not apply to searches of data on cell phones).

The intensity of the search is:


start ... probable causeincident to arresttiming

The timing of a search incident to arrest must be reasonable under the circumstances, but it may take place immediately before the arrest, Rawlings v. Kentucky, 448 U.S. 98, 111 (1980), or some considerable time after it. United States v. Edwards, 415 U.S. 800, 805 (1974) (ten hours). If the warrantless search takes place before the arrest, and provides the probable cause for the subsequent arrest, the prior warrantless search must be grounded on some other exception. That initial search may not be justified as a search incident to arrest. Smith v. Ohio, 494 U.S. 541, 543 (1990). The timing of the search:


start ... lawful stopprobable causeautomobile exception

"The police may search an automobile and the containers within it where they have probable cause to believe contraband or evidence is contained." California v. Acevedo, 500 U.S. 565, 580 (1991). This includes containers belonging to passengers. Wyoming v. Houghton, 526 U.S. 295 (1999). This automobile exception includes motor homes in a "place not regularly used for residential purposes—temporary or otherwise."

Police may seize a cell phone, but a search warrant or exigent circumstances is required before viewing the data. See Riley v. California, 134 S.Ct. 2473 (2014).

The police may, if they wish, impound the car and search it on police premises without a showing of exigent circumstances. Chambers v. Maroney, 399 U.S. 42, 52 n.10 (1970); Florida v. Meyers, 466 U.S. 380, 382 (1984).

It likely does not matter if the driver stops the car within the curtilage of the defendant's home if the police are in hot pursuit. See the discussion of Scher v. United States, 305 U.S. 251 (1938), in Collins v. Virginia, 584 U.S. ___ (2018).


start ... reasonable expectation of privacy?

The evidence was seized in violation of the Fourth Amendment. However, the evidence will only be suppressed if police infringe an interest of the defendant which the Fourth Amendment was designed to protect. This is referred to as a "reasonable expectation of privacy," or less accurately, "standing."

One who owns or lawfully possesses or controls property generally has a legitimate expectation of privacy by virtue of the right to exclude others. Byrd v. United States 138 S.Ct. 1518 (2018) (unauthorized driver of a rental car may contest search). However, car thieves do not have a reasonable expectation of privacy in a stolen car. Id. at 1529.

Passengers are seized in traffic stops, and thus may contest the legality of the stop (and the fruits thereof). See Brendlin v. California, 551 U.S. 249, 258 (2007). If the stop is lawful, passengers may not contest a seizure of incriminating evidence taken from the vehicle unless they claim to own the vehicle or the evidence. Rakas v. Illinois, 439 U.S. 128, 139-40 (1978).

The defendant:


The evidence is illegally seized, and a motion to suppress should be granted.

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The search of the person was lawful.

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The search of the vehicle was lawful.

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Suppression of evidence is not available as a remedy.

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The described search does not violate the Fourth Amendment.

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