A cell phone must connect to a group of antennas, called a cell site, to be usable. When it connects with a cell site, Cell-Site Location Information (CSLI) is generated and collected by cell service providers. Such information includes the phone number, the identification number of the cell site, and the date and time of the connection. Because a cell phone usually connects with the nearest cell site, CSLI can also indicate the approximate location of a cell phone consistently. Law enforcement often seeks to access to CSLI from cell service providers for the purpose of criminal investigations and evidence collections, e.g. tracking physical movements of a suspect. In Carpenter v. United States (2018), the Supreme Court of the United States held that seven-day historical CSLI obtained from the cell service providers by the law enforcement was the product of a search under the Fourth Amendment to the U.S. Constitution. This article aims to provide facts and decision of Carpenter. It also examines how interpretation of a searché under the Fourth Amendment has been evolved. Finally, the possible consequence of Carpenter will be analyzed.