The history of photography in the service of science is also the history of the way in which photographs have sometimes been manipulated to prove a variety of scientific and quasi-scientific claims. Duchenne de Boulogne's photographs of patients receiving electric shocks were offered as evidence that individuality played little part in the expression of emotion and, by extension, behavior. The naturalist Louis Agassiz collected daguerreotypes to further his study of racial differences and the revelatory nature of external distinguishing featuresand to bolster his belief that the white European male was a superior species. The Italian anthropologist Cesare Lombroso subscribed to a theory that viewed the criminal as an example of reversion to a primitive type and illustrated his discussions with photographs of what he considered to be such types: epileptics and murderers, as well as tattooed criminals. Sir Francis Galton's composite portraiture, based on merging physical characteristics of groups of individuals into a single picture, was proffered as a tool to visualize such "deviants" as the insane and the criminal.

Such conjectures were largely ignored by those involved in apprehending the criminal as they offered little in the way of practical assistance to the police. In 1872, however, the French police adopted an anthropometric system devised by Alphonse Bertillon, whose portraits parlés (speaking likenesses) delineated individual rather than general characteristics of a criminal's anatomy. Developed to assist in the apprehension of recurrent criminals, the system was based on a series of measurements Bertillon considered unique to each body and included descriptions of characteristic markings accompanied by photographs. By 1893, his system had been widely adopted by police departments in both Europe and the United States and contributed to a standardization of police methods.