Before a newly-elected government abandoned the project in 2010, for at least eight years the British state actively sought to introduce a mandatory national identification scheme for which the science and technology of biometrics was central. Throughout the effort, government representatives attempted to portray biometrics as a technology that was easily understandable and readily accepted by the public. However, neither task was straightforward. Instead, particular publics emerged that showed biometric technology was rarely well understood and often disagreeable. In contrast to some traditional conceptualizations of the relationship between public understanding and science, it was often those entities that best understood the technology that found it least acceptable, rather than those populations that lacked knowledge. This paper analyzes the discourses that pervaded the case in order to untangle how various publics are formed and exhibit differing, conflicting understandings of a novel technology.