This paper considers the use of the products of surveillance, primarily images, as evidence within the criminal trial. These products, whether static images, video or voice recordings, are increasingly being mediated for the fact-finder via 'experts', proffering an opinion about the meaning of some surveillance image, artefact or trace. Common law courts, including those in Australia, the UK, Canada, and the US, have been surprisingly accommodating towards such evidence-allowing incriminating opinions to be presented by witnesses with questionable or unsubstantiated 'expertise'. Institutional and judicial responses tend to be inattentive to the reliability of such evidence, and display a misplaced faith in the capacity of traditional trial safeguards to expose and manage the weaknesses inherent in this type of evidence. In looking at the ways in which courts use CCTV images, voice recordings and other traces generated by surveillant assemblages, this paper offers a legal site for consideration that has not featured prominently in recent surveillance literature. It suggests that the preoccupations generated by the ubiquitous nature of everyday surveillance do not always map cleanly onto the use of surveillance artefacts in the criminal justice system. At the same time this paper explores how ideas and concepts familiar to the analysis of surveillance techniques, cultures, imaginaries and practices might inform our understanding of the criminal trial and its related processes. Fundamentally concerned with the value of such evidence, this paper argues that given the premium placed upon accuracy and fairness within the criminal trial, the state should be able to guarantee the basic trustworthiness of 'expert' opinions before interpretations derived from surveillant assemblages are admitted to assist with proof of identity and guilt.