When expert opinion evidence goes wrong

  • Douglas WaltonEmail author
Original Research


This paper combines three computational argumentation systems to model the sequence of argumentation in a famous murder trial and the appeal procedure that followed. The paper shows how the argumentation scheme for argument from expert opinion can be built into a testing procedure whereby an argument graph is used to interpret, analyze and evaluate evidence-based natural language argumentation of the kind found in a trial. It is shown how a computational argumentation system can do this by combining argument schemes with argumentation graphs. Frighteningly, it is also shown by this example that when there are potentially confusing conflicting arguments from expert opinion, a jury can only too easily accept a conclusion prematurely before considering critical questions that need to be asked.


Unjust conviction Expert opinion evidence Ad verecundiam fallacy Faulty legal reasoning Hybrid system Carneades argumentation system 



The author would like to thank the Social Sciences and Humanities Research Council of Canada for support from Insight Grant 435-2012-0104: The Carneades Argumentation System. I would like to thank my PhD student Waleed Mebane for help in constructing figure 10. I would also like to thank my colleagues Ron Allen, Michal Araszkiewicz and Bart Verheij. They made especially helpful comments after an earlier version of this paper was read at the Conference on Legal Evidence held in Lisbon in 2017.


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Centre for Research in Argumentation, Reasoning and RhetoricUniversity of WindsorWindsorCanada
  2. 2.Philosophy DepartmentUniversity of WindsorWindsorCanada

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