In this article I examine how psychologists, amateurs and actors in the police and in juridical fields positioned themselves in the 1920s and 1930s on the scientific nature of graphology. Graphology, the study of the character from handwriting, was linked with the hope of providing reliable methods for the investigation of psychological states and dispositions. The essay argues that on an epistemic level two different models have been represented to support the scientific nature of graphology: for one thing resorting to (...) the special individual skill, the “genius” of a graphologist; or rather depersonalized techniques predominantly based on statistics. Amateur graphologists used both of these forms.On a methodological level, I argue that in order to historicize the human sciences in general, and psychology in particular, it is useful to examine the translation processes that turn everyday interpretative practices (of facial expressions, dreams, handwriting) into scientific legitimate investigative procedures. In order to investigate precisely this translation process, it is useful to look at what Thomas Gieryn calls “boundary work” at the border between scientific and non-scientific interpretation practices, for which graphology is used here as an example. It is particularly illuminating to examine how representatives of the official sciences distinguish themselves from presumed “charlatans”, which is why the article focuses on court cases and the demarcation strategies used by the police against fraudulent amateur graphologists. (shrink)