An Argumentation Interface for Expert Opinion Evidence

• Author: Nanning Zhang,Douglas Walton
• Date: 01 March 2016
• DOI: http://doi.org/10.1111/raju.12115
• Published date: 01 March 2016

An Argumentation Interface

for Expert Opinion Evidence

DOUGLAS WALTON and NANNING ZHANG*

Abstract. Tribunals have come to depend increasingly on expertise for determining

the facts in cases. However, current legal methods have proved problematic to work

with. This paper argues that, as a special model of public understanding of science,

assessing expertise should consider source credibility of expertise from internal

aspects, including scientific validity and reliability, and external aspects involving

the credibility of experts. Using the Carneades Argumentation System we show that

the internal and the external aspects are mediated by the structure of the argument

from expert opinionwith its matching set of critical questions.

1. Introduction

Because the factual truths in dispute often go beyond what the fact-finders can

be expected to know, tribunals have come increasingly to depend on expertise

for determining the facts in cases. It is important to know whether jurors can be

trusted to properly assess expertise, and what decision aids might assist them in

this task. For more than four decades, researchers have studied the ways that

people process witness testimony on the model of judicial decision-making based

on evidence (Pennington and Hastie 1993), but few of these studies focus on the

intrapersonal status of fact-finders to process expertise in a rational manner. The

Daubert criteria have proved problematic to work with, and even though subse-

quent rulings have made further modifications, the whole area of expert testi-

mony evidence remains in an unsatisfactory state (Walton 2008, 265). This paper

provides a different analytic framework for fact-finders to assess and respond to

expertise in the courtroom. In Section 2, the paper critically reviews current

methods and their quandaries in the assessment of expertise and argues that

assessing expertise requires a special model of public understanding of science.

Based on this presumption, Section 3 elaborates the source credibility of expertise

from internal aspects, which includes scientific validity and reliability, and

* Funding: National Natural Science Foundation of China (71371188): On Evidence Evaluation

Model and its Application, a Study based on Decision-making in Management and in Court.

Social Sciences and Humanities Research Council of Canada, Research Grant 410-2008-0065:

Argumentationin Artificial Intelligenceand Law.

V

C2016 The Author. Ratio Juris V

C2016 John Wiley & Sons Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main

Street, Malden 02148, USA.

Ratio Juris. Vol. 29 No. 1 March 2016 (59–82)

external aspects, which involve the credibility of an expert. In Section 4, a model

for the revision and justification of beliefs about expertise is developed. It shows

how a rational response to expertise is belief revision based on the fact-finders’

subjective intrapersonal assessment of argument from expert opinion in the given

case.

2. Current Legal Methods for Assessing Expertise in the Courtroom

and their Quandaries

2.1. From Frye to Post-Daubert

The first systematic attempt to set out requirements for the admissibility and accep-

tance of evidence based on expert opinion testimony had not been established until

1923 in Frye v. United States, and the subsequent Daubert trilogy of cases extending

this method. In Frye v. United States, which involved a murder trial in which the

defendant sought to demonstrate his innocence through the admission of a lie

detector test that measured systolic blood pressure, the court announced that a

novel scientific technique “must be sufficiently established to have gained general

acceptance in the particular field in which it belongs.” In Daubert v. Merrell Dow

Pharmaceuticals, Inc., the Supreme Court explained that in order for expert testi-

mony to be considered reliable, the expert must have derived his or her conclu-

sions from the scientific method. In explaining this evidentiary standard, the

Daubert Court pointed to several factors that should be considered by a trial judge:

(1) whether a theory or technique can be (and has been) tested; (2) whether the

theory or technique has been subjected to peer review and publication; (3) the

known or potential rate of error of a particular scientific technique; (4) the existence

and maintenance of standards controlling the technique’s operation; and (5) a sci-

entific technique’s degree of acceptance within a relevant scientific community. A

critical difference between Daubert and Frye is the shift from proxy criteria for

assessing scientific evidence to a direct judicial inquiry into scientific validity

(Black et al. 1994, 715). Frye, on its face, does not ask the judge to decide whether

the evidence is reliable, but whether the expert community deems it reliable, while

Daubert requires the judge to personally assess the reliability of the evidence

(Mnookin 2007, 764).

In Kumho Tire Co. v. Carmichael, the Supreme Court shifted the question whether

an instance of expert testimony is “scientific” to whether it is “reliable.” In the

post-Daubert era, when the new Rule 702 of the Federal Rules of Evidence (FRE 702

henceforth) was written, the key term is “knowledge,” not “scientific.”

2.2. The Quandaries of Current Legal Methods

The notion of a quandary is an epistemic concept relating to evidence-based knowl-

edge in conditions of uncertainty where the given evidence is insufficient to know

what to do. In the sense we use the term in this paper, a quandary is a given eviden-

tial situation of difficulty or perplexity in which there is a difficult decision or

choice where the evidence is insufficient to know what to decide. Our definition of

this key term is based on an argumentation framework, that is, a situation where

(1) there is a conflict of opinions between two (or more, in some cases) propositions

60 Douglas Walton and Nanning Zhang

V

C2016 The Author. Ratio Juris V

C2016 John Wiley & Sons Ltd. Ratio Juris, Vol. 29, No. 1