Date of Award

January 2016

Degree Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Patricia Sullivan

Committee Member 1

Jennifer Bay

Committee Member 2

Thomas Rickert

Committee Member 3

Mark Hannah


While providing expert testimony in jury trials, scientists face an array of conflicting legal requirements. Expert witnesses must demonstrate the soundness of their scientific methodology, but they must do so with little or no reference to the literature of their field. They must explain advanced scientific concepts while phrasing their explanations as a direct response to a lawyer's question. This project examines the rhetorical strategies expert witnesses utilize as they negotiate these conflicting requirements. Previous studies have examined persuasive discourse created for and by members of an scientific academic discipline, but my study examines how scientists defend their knowledge making practices to public audiences in a highly pressurized, overtly agnostic setting. My study also features a distinctive emphasis on the portions of expert testimony in which expert witnesses describe and defend the scientific methodologies that under-gird the evidence they present to the jury. To analyze these statements, I combine a Toulminian coding system with one developed to analyze assertions of expertise made in non-academic contexts. I identify four distinct challenges expert witnesses face. I then trace the origins of these challenges to differences in the processes through which lawyers and scientists are professionalized. I elucidate the implications these challenges have for our justice system, for the scientific community, and for technical communication scholars.