Facial recognition-a type of biometric technology-mimics how people identify or verify others by examining their faces. Recent advancements have increased the accuracy of automated FRT resulting in increased use across a range of applications. As the use of facial recognition technology (FRT) continues to expand, it has become increasingly important to understand its use across the federal government in a comprehensive way. Law enforcement agencies' use of FRT has received increased attention from policymakers and the public. Some of the concerns raised revolve around the accuracy of the technology, including potential race-, gender-, and age-related biases; the process of collecting, retaining, and securing images contained in various facial recognition databases; public notification of the use of facial recognition and other image-capturing technology; and policies or standards governing law enforcement agencies' use of the technology. Some of these concerns have manifested in actions such as federal, state, and city efforts to prohibit or bound law enforcement agencies' use of FRT. In addition, some companies producing facial recognition software have placed new barriers to law enforcement using their technologies. This book provides an overview of federal law enforcement agencies' use of FRT, including the current status of scientific standards for its use.