CRS In Focus, IF13068, July 21, 2025. “Automated license plate readers (ALPRs) are camera systems that capture the license plate data of vehicles, along with related information. They are generally available in fixed and mobile formats. Fixed ALPR systems are mounted in specific locations, often using existing infrastructure such as light poles, traffic lights, buildings, or bridges. Mobile ALPR systems are frequently mounted on police vehicles or privately contracted vehicles. Although details vary by system and jurisdiction, information obtained from ALPR systems may be included in certain databases—whether maintained by public or private entities—that are accessible or searchable by law enforcement. Law enforcement agencies use ALPRs for a variety of proactive and reactive policing purposes, including to gather intelligence and evidence, help identify potential suspects, and facilitate crime scene analysis. Law enforcement use of ALPRs raises a range of questions for policymakers and the public. For instance, one consideration is how ALPR use may, while aiding criminal investigations, potentially infringe upon individuals’ privacy and civil liberties—in particular, Fourth Amendment protections from unreasonable searches and seizures. In general, courts have found that “mere observation” of an object in plain view does not implicate the Fourth Amendment, which suggests that law enforcement’s initial reading of a license plate using an ALPR is ordinarily not a Fourth Amendment search absent additional circumstances. The ALPR caselaw typically focuses instead on the related question of whether law enforcement queries of certain databases containing ALPR information amount to a Fourth Amendment search. No federal appellate court has decided that issue, although one circuit court judge discussed it in a concurrence. A number of federal trial courts and some state courts have upheld law enforcement access to such databases, while cautioning that warrantless surveillance through ALPRs could violate the Fourth Amendment in some circumstances. This In Focus provides an overview of ALPRs, select Fourth Amendment caselaw on their use, and congressional considerations…”