Can there be a burden of the best explanation?
| DOI | 10.1177/1365712718765539 |
| Published date | 01 April 2018 |
| Date | 01 April 2018 |
| Subject Matter | Articles |
Article
Can there be a burden
of the best explanation?
Gustavo Ribeiro
Lecturer at Boston University Law School, Boston, MA, USA and Associate at Greenberg Traurig, LLP
Abstract
In this article I address a foundational question in evidence law: how should judges and jurors reason
with evidence? According to a widely accepted approach, legal fact-finding should involve a
determination of whether each cause of action is proven to a specific probability. In most civil cases,
the party carrying the burden of persuasion is said to need to persuade triers that the facts she needs
to prevail are “more likely than not” true. The problem is that this approach is both a descriptively
and normatively inadequate account of reasoning with evidence in law. It does not offer a plausible
picture of how people in general, and legal fact-finders in particular, reason with evidence. And it
turns out that if we try to do what the approach tells us, we end up with absurd results. Faced with
these difficulties, a group of evidence scholars has proposed an alternative. According to them, legal
fact-finding should involve a determination of which hypothesis best explains the admitted evidence,
rather than whether each cause of action is proven to a specific probability. My main contributions in
this article are twofold. First, I elaborate on the many descriptive, normative and explanatory
considerations in support of an explanation-based approach to standards. Second, I offer novel
replies to pressing objections against that same approach.
Keywords
abduction, epistemology, evidence, explanation, standard of proof
Introduction
A party who bears the burden of persuasion can win only if the evidence persuades the triers of the
existence of the facts she needs to prevail under the requisite standard of proof (Mueller and Kirkpatrick,
2011: 645). Exactly how to understand the different standards of proof is controversial, however. This
article contributes to this debate by offering a new defence to an explanation-based approach to stan-
dards. It does so in two main ways. First, by replying to a potentially powerful objection. Second, by
offering a revised formulation of standards in explanatory terms to clarify the confusion.
According to a widely accepted approach, standards of proof should be understood as probability
thresholds that correspond to a numerical degree of subjective confidence that the judge or juror must
Corresponding author:
Gustavo Ribeiro, Lecturer at Boston University Law School, Boston, MA, USA and Associate at Greenberg Traurig, LLP.
E-mail: gustavor@bu.edu
The International Journalof
Evidence & Proof
2018, Vol. 22(2) 91–123
ªThe Author(s) 2018
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DOI: 10.1177/1365712718765539
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reach on each element of the claim to justify a verdict for the party carrying the burden of persuasion
(see, for example, Finkelstein and Fairley, 1970; Hamer, 2004; Kaplan, 1968; Kaye, 1999; Koehler and
Shaviro, 1990; Lempert, 1977; Redmayne, 2008). For instance, thi s interpretation assumes that the
preponderance of the evidence standard applicable in most of the civil cases in the United States simply
means ‘proven by a probability higher than 0.5’.
In recent decades, however, commentators have raised several objections to probability approaches to
standards of proof (see, for example, Allen, 1986, 1991; Allen and Leiter, 2001; Cohen, 1977; Nesson,
1979, 1985; Pardo, 2013; Tribe, 1971). We can divide these objections into two camps. The first group
suggests that the most common subjective probabilistic frameworks that evidence scholars relied upon
are descriptively and normatively inadequate. These probabilistic frameworks do not offer a plausible
picture of how people in general, and legal fact-finders in particular, reason with evidence. Moreover,
following this approach leads to absurd results. The second group of objections focuses on internal
limitations to probability approaches to standards of proof. These include so-called ‘proof-paradoxes’.
These objections make a strong case against a probability-based approach to standards.
A group of evidence law scholars has proposed an alternative. According to them, legal fact-finding
should involve det ermining the best explanation o ft he admitted evidence, rather th an proving each element
to a specific probability (see, for example, Allen, 2008,2014; Allen and Jehl, 2003; Allenand Pardo, 2007;
Pardoand Allen, 2008). The idea,in a nutshell, is that fact-finders shouldinfer the truth of a givenhypothesis
(outof the set of hypothesesoffered by the partiesor constructed by thefact-finders) fromthe fact that it ‘best
explains’ (as defined blow) the admitted evidence and thendecide the case based on that inference.
Under this alternative view of standards, inference to the best explanation (hereinafter ‘IBE’)
becomes the characteristic mode of inference in legal fact-finding. IBE can be characterised as follows.
1
First, when faced with an unexplained phenomenon, we select a group of plausible hypotheses that we
determine explain a given phenomenon. We never begin with a full menu of all possible potential
explanations. We also do not consider a randomly generated class of explanations. Not only are the
plausible hypotheses compatible with many of our background beliefs, but we also believe that, if true,
they would explain an aspect of the phenomenon being addressed. We then infer the (probable) truth
from that hypothesis which provides the best explanation.
A difficulty with such explanation-based approaches to standards of proof is that the epistemology
and philosophy of science literature are filled with attacks and defences of IBE as an epistemically
justified mode of inference. While some authors praise IBE as an indispensable mode of inference for
science, others claim that it is unclear how explanatory value can get us closer to the truth.
2
That is, it
might be difficult to see why the mere fact that a given hypothesis best explains a phenomenon makes
that hypothesis more likely to be true.
Proponents of explanation-based approaches to standards have rebutted similar objections to IBE by
claiming that the same objections also apply to all forms of inductive reasoning (Pardo and Allen, 2008).
Unless we are willing to accept skepticism about induction in general, we ought to reject these objec-
tions. The problem here is that, unless we are already committed to a non-skeptic position, this reply is
not very convincing. We then need a better defence of IBE. This article provides just that. First, it offersa
reply to this objection. In a nutshell, the reply notes that elements of explanatory virtues and inferential
1. American philosopher Charles Peirce first identified inference to the best explanation as a distinctive mode of inference. Peirce
used the term ‘abduction’ instead of inference to the best explanation, a term many still use. See, e.g., Peirce (2012). This
assertion is controversial, however. Some Peirce scholars claim that abduction and IBE are actually different forms of reasoning
(Campos, 2011). This historical debate should not concern us here. Gilbert Harman coined the term ‘inference to the best
explanation’ (Harman, 1965). Many philosophers have used the idea in different debates, such as in discussions concerning
moral nihilism in metaethics (Harman, 1977), rejections of skepticism about the external world in epistemology (Vogel, 1990)
and realism in philosophy of science (Putnam, 1979). To date, Peter Lipton provided the most comprehensive account and
defence of inference to the best explanation (Lipton, 2004). This section draws heavily on Lipton’s superb book.
2. See, e.g., Lipton (2004) and Kelly (2001). But see also Nozick (1994), Van Fraassen (1989) and Fumerton (1992).
92 The International Journal of Evidence & Proof 22(2)
virtues coincide, which means that if the latter is truth-conducive (and, therefore, allows us to infer
epistemically justified propositions), so is the former. This article’s second contribution relates to the
specific formulations of standards of proof and other evidentiary mechanisms that should follow from
adopting an explanatory framework. How exactly should triers reason under an explanation-based
approach? What does it mean to ‘select the best explanation’ in legal settings? Commentators suggest
that fact-finders should decide cases based on the relative plausibility of the stories put forth by the
parties or by the triers themselves (Pardo and Allen, 2008). The best way to understand this prescription
is that fact-finders should decide cases based on the relative explanatory value of the evidentiary
hypothesis presented by the parties or the triers themselves. Based on this accepted hypothesis, fact-
finders should infer the best explanation and find for the party that substantive law supports. Under this
formulation, standards of proof are more clearly designed to set up different thresholds of explanatory
values that the party carrying the burden of persuasion needs to meet. The higher the standard, the more
valuable the explanation (for the best evidentiary hypothesis available to triers) must be.
Descriptive, normative and explanatory considerations support an explanation-based approach to stan-
dards. Proponents of the explanation-based approach highlight how the approach better describes jurors’
reasoning (Allen, 2008, 2014; Allen and Jehl, 2003; Allen and Pardo, 2007; Pardo and Allen, 2008). To
support thisconclusion, proponents offerevidence that what the approachasks of jurors is compatiblewith
psychological research on jury decision-making (see, for example, Pennington and Hastie, 1988, 1991,
1992, 1993a, 1993b). The primary finding of that research is that individuals do not usually reason with
separate piecesof evidence, which is contrary to what the probabilistic approachto standards of proof says
of jurors. Instead, people tendto construct an entire storythat will fit the evidence and thenmake decisions
based on the explanatory virtue of that story. There are also important normative considerations that
support an explanation-based approach to standards. Not only do explanation-based approaches avoid
some of the problems associated with probabilistic approaches, but explanation-based approaches also
improve by prioritising evidential support over subjective credence.
3
Moreover, explanatory considera-
tions also favour explanation-based approaches. In particular, they allow for a better understanding of
different evidentiary mechanisms, including the concepts of ‘relevance’ and ‘probative value’.
At the same time, there are pressing objections against explanation-based approaches to standards.
This article addresses some of the most significant ones. For example, some argue that an explanationist
approach incentivises parties to overload courts with evidence. This is because parties would view their
role as one of presenting overreaching narratives, and so would be more inclined to offer evidence that
speaks to parts of the narratives but is only marginally (if at all) related to controversial facts in the case.
This ‘evidence saturation’ could, in turn, ma ke legal decision-making more complex such that the
explanation-based approach ultimately becomes too costly or unworkable. Even if we concede to the
objector and assume that the app roach does, in fact, create the se incentives (which is not ent irely
convincing), we still have reason to believ e that the approach will not turn out to be unworka ble.
Specifically, other evidentiary mechanisms can combat evidence saturation. Admissibility and exclu-
sionary rules are the best examples. Not only do are there a myriad rules that make evidence inad-
missible, but there is also a catch-all exclusionary clause in Federal Rule of Evidence 403.
4
Significant practical implications turn on this debate. The goal of achieving a sufficient degree of
factual accuracy is a fundamental part of all legal systems. Any assignment of entitlements and their
correlative disablements depends on sufficiently accurate fact-finding.
5
In a contractual dispute, a
sufficiently accurate factual finding is essential to determine whether the act that constitutes an alleged
breach took place. The legitimacy of any assignment of entitlements and disablements also depends on
3. See Laudan (2006: 79), quoted in n 18 below.
4. For a ‘collectivist’ treatment of Federal Rule of Evidence, see, e.g., Old Chief vU.S. 519 U.S. 172 (1997).
5. For a seminal discussion of entitlements and disablements and their correlatives see Hohfeld (1913, 1917). For a more con-
temporary discussion of the centrality of burdens and standards of proof for individuals’ entitlements see Symposium on
presumptions and burdens of proof (1994) Harvard Journal of Law and Public Policy 17(3).
Ribeiro 93
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