Drivers may have a reasonable expectation of privacy in a rental car, even though the rental agreement did not authorize them to drive the car, the U.S. Supreme Court ruled May 14 in Byrd v. United States.
Terrance Byrd was driving a rental car when he was stopped by police for a traffic stop.  The car had been rented by another person.  Byrd was not an authorized driver under the rental agreement.
Police told Byrd they did not need his consent to search the car because he was not an authorized user.  Police found drugs and illegal body armor in the trunk.
Byrd moved to suppress the drugs and body armor, but the District Court ruled that Byrd lacked a reasonable expectation of privacy in the car because he was not an authorized user.  The Third Circuit affirmed.
The Supreme Court granted cert. to resolve a circuit split on this issue.
Reasonable expectation of privacy applies
In a unanimous opinion, the Court held that “as a general rule, someone in otherwise lawful possession and control of a rental car has a reasonable expectation of privacy in it even if the rental agreement does not list him or her as an authorized driver.”
Whether a person has a reasonable expectation of privacy is based on the property right to “exclude others” from the property, the Court said. 
“The Court sees no reason why the expectation of privacy that comes from lawful possession and control and the attendant right to exclude would differ depending on whether the car in question is rented or privately owned by someone other than the person in current possession of it.”
The rental agreement, which made Byrd an unauthorized driver, merely allocated private risk among the parties on issues such as liability, but did “not eliminate an expectation of privacy” under the Fourth Amendment, the Court said.
But the Court emphasized that Byrd must have “lawful possession” of the car in order to have an expectation of privacy.  The Court analogized to a burglar in a house, who may have a “subjective expectation” of privacy in the house, “but not one which the law recognizes as ‘legitimate.’”  Likewise, a “car thief would not have a reasonable expectation of privacy in a stolen car,” the Court said.
The Government argued that Byrd did not have lawful possession of the car because he engaged in a fraudulent scheme to rent it, and also that there was probable cause to search the car in any event.  The Court remanded the case for consideration of these arguments in the first instance.
Concurring opinions
Justice Thomas, joined by Justice Gorsuch, concurred.  They said, however, that they had “serious doubts about the ‘reasonable expectation of privacy’ test from Katz v. United States” but that “no party has asked us to reconsider.”
Since the Fourth Amendment protects people from unreasonable search and seizure of “their effects,” they would focus on what kind of property interest a person must have to assert a Fourth Amendment claim.
Justice Alito also concurred, but interpreted the opinion narrowly to hold only that “an unauthorized driver of a rental car is not always barred from contesting a search of the vehicle.”  He said lower courts should be able to consider the terms of the rental agreement, the circumstances surrounding the rental, why the driver had possession of the car, and the legality of the driver’s conduct under State laws, in deciding whether a driver can assert a Fourth Amendment claim.