Computers, Privacy & the Constitution

Reasonable Expectation of Privacy after Carpenter--Some thoughts about this article

-- By SayakaSekimiya - 05 Mar 2020


It has been said that the development of technology has created a danger to our privacy. It is true that technologies have allowed the government or private companies to look into one’s private life. For example, just looking through one’s smartphone can reveal almost everything about the person’s life—such as the owner’s location, communication history, internet search history, medical records, etc. Upon such development of information society, this article suggests that the courts drop the reasonable expectation test in dealing with the Fourth Amendment search and seizure issues. He points out that the test does not protect us from the invasion of privacy today, because we do not believe that our information is private and thus, we do not have a reasonable expectation. But according to Carpenter, I think the reasonable expectation test can still work to protect our privacy.

Reasonable Expectation Test under the Fourth Amendment

The Fourth Amendment provides that the people are secured in their persons, houses, papers, and effects, against unreasonable searches and seizures unless warrant supported by probable cause authorizes it. At first, the US courts relied on trespass doctrine, under which the courts focused on physical intrusion to the place. But as the style of intrusion by the government changed, the courts started to use the “reasonable expectation” test after Katz v. United States, 389 U.S. 347 (1967). Under the test, if a search violates one’s reasonable expectation of privacy, the search is considered “unreasonable” and the law enforcement agency needs a warrant. Under the test, the expectation must be reasonable both as subjectively and objectively, meaning it requires the public to consider the expectation as reasonable. By evaluating objective reasonableness, the courts are balancing our personal privacy and public safety.

Third-Party Doctrine

Under the reasonable expectation test, the courts adopt third party doctrine. Under the doctrine, the Fourth Amendment is not implicated when one shares information with a third party, and then the government obtains the information through the third party. The Supreme Court thinks that a person who shares sensitive information with a third party takes the risk that the information can be disclosed by the third party to the government, thus there is no reasonable expectation of privacy. In United States v. Miller, 425 U.S. 435 (1976), the Supreme Court held that there was no reasonable expectation of privacy in financial records held by a bank. In Smith v. Maryland, 442 U.S. 735 (1979), the Supreme Court held that a person who used the phone assumed the risk that the telephone company would reveal to the police the numbers he had dialed.

Carpenter Decision and Reasonable Expectation Today

Today, we know that our private information is being collected. When we use smartphones, companies are collecting data about our behavior. Our location, mail communication, web search history, are collected and used for commercial purposes. When we go out, surveillance cameras are watching us everywhere. By using credit cards, our purchase history is being stored. We know that such kinds of privacy might be conveyed if those companies voluntarily give them to another including the government. According to the third-party doctrine, it seems that the government can obtain such information from those companies without obtaining a warrant, since we assume the risk of disclosure by the third party company.

But knowledge of the potential risk of disclosure does not mean that we waive our privacy. Even if we do not do anything wrong, we do not want that data to be conveyed by the company to the government without any limitation. We keep using those services just because they are necessary to live today’s life. I believe most people today think the expectation that such information will not be conveyed to the government is reasonable. This idea is reflected in Carpenter.

In Carpenter v. United States, 585 U.S. __ (2018), the Supreme Court held that obtaining cell site records is a Fourth Amendment search. The court did not rely on the third-party doctrine, even though the cell site data was stored by the third party. The court held that, given the unique nature of a cell site record, i.e. a detailed and comprehensive record, the third-party doctrine does not cover it. The court explained that such data give the government near perfect surveillance. In addition, the court pointed out that “cell phones and the services...are ‘such a pervasive and insistent part of daily life’ that carrying one is indispensable to participation in modern society”. Thus, the court concluded that Carpenter had a reasonable expectation of privacy in the records and the third party doctrine did not apply to this case.

Carpenter shows that the court does not apply the third-party doctrine automatically. Even if we assume the potential risk that our information can be disclosed through a third party, the court will examine whether we have a reasonable expectation in the information by looking at the characteristics of the data under the reasonable expectation test. The test can still protect our privacy in today’s digital age.


Since the Supreme Court shows that it does not automatically apply the third-party doctrine, and rather it examines the reasonable expectation by looking at the characteristics of privacy intruded, the test can still work today. One might argue that it is not clear to what extent the expectation of privacy is “reasonable” in today’s digital age. However, since the Fourth Amendment authorizes the government to conduct searches as long as they are reasonable, I think the standard to deal with the Fourth Amendment issues cannot be crystal clear, and the reasonable expectation test is a practical standard so far.

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r1 - 05 Mar 2020 - 13:17:06 - SayakaSekimiya
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