To what extend is crime-related behavior a product of nature? The question has haunted the criminology discipline and has motivated many studies that have tried to assess, in a more or less deterministic and mechanical fashion, the respective weight of biological factors and social factors through heritability studies, namely research designs using twins. A few years ago, Callie Burt and Ronald Simons sent a clear message to their scientific community: "[W]e call for an end to heritability studies in criminology and recognition of the problematic nature of existing heritability estimates for criminal phenotypes. " (2014, p. 225). How can such a forceful declaration convince the colleagues and achieve the desired effect? Especially since this appeal evokes a foundational and ABSTRACT (Un)certainty is not an inherent quality of a scientific assertion. It is rather the product of negotiations and collective work performed amidst noisy or quiet scientific debates. Using a controversy on heritability of crime-related behaviors as a case study, this paper proposes an analysis of the rhetoric at play to produce (un)certainty in publications presenting competing arguments. The controversy under study is at the heart of the legitimization of biosocial criminology, a contested field of study. The research shows that on the discursive front, three main strategies are used to modalize the (un)certainty of scientific claims over that of competing ones: denial, dismissal, and displacement. On the emotion front, surprise and ridicule are used and elicited to transform scientific claims into staple pieces of knowledge. Acknowledging the strengths and uniqueness of science as a mode of knowledge, this study underlines the importance for users of science to get comfortable not only with the doubts and conflicts at its core but also with the discursive strategies that are integral to science production and communication, as well as to the legitimization of a field of study.