Mechanical Witness will be the first cultural and legal history charting the changing role and theoretical implications of the use of film and video as courtroom evidence. The author moves from the earliest uses of film in the courts of the 1920s to Osama Bin Laden's taped statements after 9/11, revealing how the courts have developed a reliance on film and video technologies and contributed to the growing influence of visual media in twentieth century America. At the same time, the meaning of film and video as used in juridical contexts has developed a theoretical legacy which both resonates with and contradicts existing scholarship--focusing on economic, social, or aesthetic factors--which hitherto has defined film's status and cultural contribution. In the context of a trial, the possible meanings of a film or video can be very different from its meaning when shown in a movie theater or broadcast on television, yet the public and cinema scholars tend to assume that the meaning of an image remains constant. Mechanical Witness demonstrates that we must understand evidentiary film and video's institutional specificity if we are to understand the effects of motion picture technologies on our culture. This study sets the terms for a long overdue assessment of how the entertainment industry has dominated and shaped our film viewing practices, the place of moving picture evidence in the courtroom, and the social and cultural consequences of these intertwined histories.