U.S. Supreme Court

Chemerinsky: A quartet of Fourth Amendment cases to watch

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Erwin Chemerinsky

Erwin Chemerinsky

Again, this year, there are a number of Fourth Amendment cases before the U.S. Supreme Court that have the potential to significantly change the law and police practices. All have been argued, so decisions could come soon.


Although it has not received the headlines that the more high-profile cases of the term have, Carpenter v. United States, which was argued on Nov. 29, could be a blockbuster ruling. Timothy Carpenter was suspected of committing a series of armed robberies. The FBI went to his cellphone company and got the cell phone tower records that revealed his location and his movements for 127 days. The FBI received this information without a warrant from a judge. The cell tower information was crucial evidence used to convict him and sentence him to 119 years in prison.

Every time we use our cellphones–to send and receive calls or texts or emails or access the internet–it connects to cell towers. The records–generated hundreds and sometimes thousands of times per day–include the precise GPS coordinates of each tower, as well as the day and time the phone tried to connect to it. It is possible to determine our location at almost any point in time and track our movements through this information. The police constantly use this technology; in 2016, Verizon and AT&T alone received about 125,000 requests for the cellular information from law enforcement agencies.

The issue in Carpenter v. United States is whether the Fourth Amendment, which prohibits unreasonable searches and arrests, requires that the police obtain a warrant to access this information. A great deal can be learned about a person from this information. As one court decision explained, “[a] person who knows all of another’s travels can deduce whether he is a weekly churchgoer, a heavy drinker, a regular at the gym, an unfaithful husband, an outpatient receiving medical treatment, an associate of particular individuals or political groups—and not just one such fact about a person, but all such facts.”

Every federal court of appeals to consider the issue has held that no warrant is required before police access cellular location information. These courts have relied on a legal principle called the “third-party doctrine”—that we have no privacy interest in information that we share with a third party, such as a phone company. For example, in Smith v. Maryland in 1978, the court held that police do not need a warrant to obtain from the phone company a record of the numbers that we dial or receive calls from because we should not be able to expect that the third party, the phone company, will keep the information secret. The court has applied this to say that the police can obtain our banking information, such as records of our deposits and withdrawals, without a warrant because a third party (the bank) has the information.

As Justice Sonia Sotomayor pointed out in her separate opinion in United States v. Jones, the third-party doctrine “is ill suited to the digital age.” The ability of the police to track our movements through technology is constantly expanding and Carpenter will be important in determining whether there are Fourth Amendment limits on the police.


Two cases concerning motor vehicles (a rental car and a motorcycle) and the Fourth Amendment were argued Jan. 9. In Byrd v. United States, the court is considering “[w]hether a driver has a reasonable expectation of privacy in a rental car when he has the renter’s permission to drive the car but is not listed as an authorized driver on the rental agreement.”

Latasha Reed rented a car in New Jersey. Reed signed a rental agreement that indicated that additional drivers were only permitted “with prior written consent.” Nonetheless, Reed allowed her boyfriend, Terrence Byrd, to drive the car. Byrd drove out of state and was pulled over in Harrisburg, Pennsylvania, by police. He was given a warning about driving in the left lane. The officers saw that Byrd’s name was not on the rental car agreement and they searched the car. In the trunk of the car, the troopers found a laundry bag that contained 49 bricks of heroin.

Byrd argued that the police search violated the Fourth Amendment. The federal district court rejected that argument, concluding that Byrd could not have had a reasonable expectation of privacy in the car because he was not on the rental car agreement. Byrd pleaded guilty and was sentenced to 10 years in prison. The Philadelphia-based 3rd U.S. Circuit Court of Appeals affirmed.

The underlying issues are fascinating. The Supreme Court long has discarded the question of who has “standing” to challenge a police search, but underlying this case is whether the court will revive that. How is the reasonable expectation of privacy to be determined in this context? Should the rental car agreement matter for Fourth Amendment analysis?

The question in Collins v. Virginia is “[w]hether the Fourth Amendment’s automobile exception permits a police officer, uninvited and without a warrant, to enter private property, approach a house and search a vehicle parked a few feet from the house.”

The case stems from a high-speed chase in Virginia. Officers pursued a motorcycle that was traveling more than 140 mph. The motorcycle got away, but by using social media the police officers found reason to believe that the motorcycle belonged to Ryan Collins, and was parked at a house where he stayed. The officers went to the house and up the driveway. They saw a covered motorcycle, and lifted it to find the orange and black Suzuki they were seeking.

Collins argued that the police violated the Fourth Amendment in going onto the property without a warrant. But the Virginia courts rejected that argument, with the state supreme court concluding that the automobile exception to the warrant requirement applied. The case comes down to some basic questions: Is it enough that the officers thought that the motorcycle, a motor vehicle, contained evidence of a crime? Or did the police violate the Fourth Amendment by entering on to private property and lifting the cover on the motorcycle?


Carpenter, Byrd, and Collins all involve criminal defendants challenging police searches. The final Fourth Amendment case of the term, District of Columbia v. Wesby, decided Jan. 22, arose in the context of a civil suit.

Police in Washington, D.C. received a complaint about loud music in a house that was thought to be vacant. The police entered and saw the house was in disarray. There was almost no furniture downstairs. The police officers smelled marijuana and saw beer bottles and cups of liquor on the floor. The court noted, “In the living room, the officers found a makeshift strip club. Several women were wearing only bras and thongs, with cash tucked into their garter belts. The women were giving lap dances while other partygoers watched. … The officers found more debauchery upstairs. A naked woman and several men were in the bedroom. A bare mattress—the only one in the house—was on the floor, along with some lit candles and multiple open condom wrappers. A used condom was on the windowsill.”

The officers questioned those present, and two individuals identified “Peaches” as the owner of the house and said that she had given permission to be there. The officers talked to Peaches by telephone. Initially she said she was renting the house and had given the partygoers permission to have the party, but she then admitted that she did not have permission to use the house. The police reached the owner and he said that that he had not given anyone permission to be there.

The officers arrested the partygoers for unlawful entry. The charges ultimately were dismissed, but several individuals sued for false arrest under the Fourth Amendment and District law. The lower courts ruled in favor of the plaintiffs, but the Supreme Court unanimously reversed. Justice Clarence Thomas wrote for the court.

First, the court said the police had probable cause for the arrest. Thomas wrote: “Viewing these circumstances as a whole, a reasonable officer could conclude that there was probable cause to believe the partygoers knew they did not have permission to be in the house.”

Second, the court concluded that even if there was not probable cause for the arrest, the officers were protected by qualified immunity, which precludes suits for money damages unless the officers violate clearly established law that every reasonable officer should know. The court said: “Even assuming the officers lacked actual probable cause to arrest the partygoers, the officers are entitled to qualified immunity because they ‘reasonably but mistakenly conclude[d] that probable cause [wa]s present.’”

District of Columbia v. Wesby did not change the law of the Fourth Amendment or qualified immunity; rather, it applied the law to a colorful set of facts. Perhaps most significant for the future, Justice Ruth Bader Ginsburg, concurring in the judgment, urged the court to reconsider a key Fourth Amendment precedent: Whren v. United States, which held the motive of the police does not matter in assessing whether there is a Fourth Amendment violation. She suggested that the court consider “in a future case, whether a police officer’s reason for acting, in at least some circumstances, should factor into the Fourth Amendment inquiry.” The court’s reconsidering Whren, could have enormous implications for the law of the Fourth Amendment.

Erwin Chemerinsky is dean of the University of California at Berkeley School of Law. He is an expert in constitutional law, federal practice, civil rights and civil liberties, and appellate litigation. He’s the author of seven books, including The Case Against the Supreme Court (Viking, 2014).

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