Rex Hammond v. United States

In Carpenter v. United States, 138 S. Ct. 2206 (2018), the Court held that the government’s use of an individual’s historical “cell site location information” (CSLI) to determine his past movements over a lengthy period of time constitutes a search within the meaning of the Fourth Amendment, requiring a warrant. But the Court expressly left open the question whether a government agent’s use of “real-time CSLI” to track a person in real time likewise constitutes a search. Id. at 2220. The question reserved in Carpenter—over which lower courts are divided—is the first question presented here: Whether a government agent’s direction to a wireless carrier to send a signal to a person’s phone, so that the phone reveals the person’s precise location and movements in real time is a search within the meaning of the Fourth Amendment.

In Illinois v. Krull, 480 U.S. 340 (1987), the Court held that the good faith exception to the exclusionary rule prevents exclusion when officers have acted “in objectively reasonable reliance on a statute” that was subsequently found unconstitutional. Id. at

But the Court “decline[d] the State’s invitation to recognize an exception for an officer who erroneously, but in good faith, believes he is acting within the scope of a statute.” Id. at 360 n.17. The question reserved in Krull—over which lower courts again are divided—is the second question presented here: Whether a government agent’s good faith but objectively incorrect reading of a statute prevents the exclusion of constitutionally tainted evidence in a criminal trial.