The book focuses on the role of expert witnesses and the discursive processes of evidence construction in the Anglo-American adversarial system. Based on a rich set of criminal trial data, it looks at epistemological positioning in expert testimony and examines its verbal and non-verbal manifestations. Drawing on the notions of stance, epistemicity and evidentiality, the book sheds light on how knowledge claims are (de)constructed and how expert testimony is turned into evidence. Unlike earlier books on courtroom discourse focusing primarily on linguistic resources, this volume highlights the persuasive and evaluative function of both linguistic and non-linguistic behaviour, showing the relevance of multimodal conduct to speaker stance and speaker positioning. The book identifies factors which help to assess the degree of scientific certainty communicated by expert witnesses as well as evaluate the plausibility of their testimony. It will be of value to forensic linguists, social scientists and legal scholars interested in the discursive mechanisms which underpin science communication and legal epistemology.