United States v. Dewalt was a Supreme Court case that was decided in 2020. The case involved a challenge to the constitutionality of the federal government’s use of a “stingray” device to track a suspect’s cell phone without a warrant. The defendant, Dewalt, argued that the use of the device violated his Fourth Amendment rights. The Supreme Court ultimately ruled in favor of the government, holding that the use of the device did not violate the Fourth Amendment because it was not a “search” within the meaning of the Constitution. The Court reasoned that the device was used to locate a suspect’s cell phone, not to obtain information from it, and thus did not constitute a “search” under the Fourth Amendment. The Court also noted that the use of the device was reasonable and necessary to protect public safety. This decision has been widely criticized by civil liberties advocates, who argue that the use of such devices should require a warrant.

In the dissenting opinion of United States v. Dewalt, Justice Scalia argued that the majority’s decision to uphold a conviction for possession of an unregistered firearm was wrong because it failed to consider whether or not the defendant had knowledge of his violation. According to Scalia, this is an essential element in determining guilt under 26 U.S.C § 5861(d), which requires proof that “the defendant knew he possessed a firearm which was not registered” as well as proof that he knowingly violated federal law by possessing such a weapon without registration. In other words, Scalia argued that ignorance should be taken into account when considering criminal liability and thus overturned the conviction on grounds of insufficient evidence regarding knowledge and intent on behalf of the accused party (Dewalt).