Between the late 19th century and the 1950s, the project of establishing a science of proof was shared by a generation of criminologists, psychologists and lawyers specializing in evidence law. Their ambition was to develop theoretical and practical knowledge of the analysis and evaluation of evidence in the courts, drawing on new knowledge established in the then-emerging fields of social psychology and forensic science and technology. All this was combined with an effort to provide judges with tools capable of guiding the rigour of their reasoning with evidence. This project, which is fundamentally interdisciplinary and breaks with a dogmatic orientation in legal analysis, was made possible by an important dialogue on both side of the Atlantic. The circulation of knowledge engaged in the science of evidence was remarkable, both in Europe and between Europe and the United States, as illustrated by the figures of Wigmore and Gorphe. The conditions that allowed the development of a science of proof project to flourish disappeared after the War and this project would not be taken on by a new generation. Research in these areas continued separately in an increasingly fragmented disciplinary landscape. This article retraces this history and sheds light on the reasons for the weakening, and the recomposition, of the science of proof at the end of the Second World War.