Civil liability and the 50%+ standard of proof

AuthorMartin Smith
DOI10.1177/13657127211011207
Published date01 July 2021
Date01 July 2021
Subject MatterArticles
Original Research Article
Civil liability and the 50%þstandard
of proof
Martin Smith
University of Edinburgh Philosophy, Edinburgh, UK
Abstract
The standard of proof applied in civil trials is the preponderance of evidence, often said to be met
when a proposition is shown to be more than 50% likely to be true. A number of theorists have
argued that this 50%þstandard is too weak—there are circumstances in which a court should
find that the defendant is not liable, even though the evidence presented makes it more than
50% likely that the plaintiff’s claim is true. In this paper, I will recapitulate the familiar arguments
for this thesis, before defending a more radical one: The 50%þstandard is also too strong
there are circumstances in which a court should find that a defendant is liable, even though the
evidence presented makes it less than 50% likely that the plaintiff’s claim is true. I will argue that
the latter thesis follows naturally from the former once we accept that the parties in a civil trial
are to be treated equally. I will conclude by sketching an alternative interpretation of the civil
standard of proof
Keywords
base rate fallacy, burden of proof, civil liability, naked statistical evidence, normic support,
preponderance of evidence, principle of equality, probability, relative plausibility
The 50%þstandard is too weak
‘Fairness’ in a criminal trial is usually associated with the granting of various protections to the
defendant—the presumption of innocence, the beyond reasonable doubt standard of proof etc. In a civil
trial, on the other hand, ‘fairness’ is usually thought to involve treating the plaintiff and defendant
equally, and ensuring that neither enjoys any special advantage over the other (see for instance Allen,
2014: section I; Brook, 1985: section II; Clermont and Sherwin, 2002: section D; Hazelhorst, 2017: ch.
4; Redmayne, 2006: section I; Winter, 1971). As a result, civil trials in common law jurisdictions are
decided according to the preponderance of evidence standard—the fact finder should side with
Corresponding author:
Martin Smith, University of Edinburgh, Philosophy, 3 Charles St, Edinburgh, EH8 9AD, UK.
E-mail: martin.smith@ed.ac.uk
The International Journalof
Evidence & Proof
ªThe Author(s) 2021
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DOI: 10.1177/13657127211011207
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2021, Vol. 25(3) 183–199
whichever party is able to produce the stronger, more persuasive body of evidence in their favour.
1
In a
tort trial, the plaintiff will typically allege that they have suffered certain harms as a direct result of the
defendant’s negligence. If the evidence in favour of this claim is stronger than the evidence against it,
then the court should find for the plaintiff. If the evidence against this claim is stronger than the evidence
in its favour, then the court should find for the defendant. The one wrinkle here is that the court should
also find for the defendant in the event that the evidence for and against the plaintiff’s claim is deemed to
be equally strong—a tolerated violation of the equality between plaintiff and defendant which we will
return to.
This set-up is often interpreted probabilistically: If the probability of the plaintiff’s claim, given the
total evidence, is greater than 50%, the court should find for the plaintiff. If the probability of the
plaintiff’s claim, given the total evidence, is 50%or less, the court should find for the defendant.
2
This
interpretation of the civil standard of proof is widely accepted—and is treated as standard in textbooks
on evidence law (see for instance, Broun et al., 1984: §339; Dennis, 2002: ch. 11, section F; Elliott and
Phipson, 1987: ch. 4, section B; Keane, 1996: ch. 3, section B;O’Malley et al., 2006: §104.01). It is also
found in case law, statutes and model jury instructi ons. Some examples (selected on no particular
basis) ...In Miller vMinister of Pensions ([1947] 2 All ER 372 at 374), Lord Denning explained the
civil standard for English law by saying: ‘If the evidence is such that the tribunal can say “we think it
more probable than not” the burden is discharged, but if the probabilities are equal it is not.” Article 140
of the Evidence Act (Cth and NSW) (1995) set out the Australian civil standard as follows: ‘In a civil
proceeding, the court must find the case of a party proved if it is satisfied that the case has been proved on
the balance of probabilities’. According to section 104.01 of the Federal Jury Practice and Instructions
for the US Federal Court System,
‘Establish by a preponderance of the evidence’ means evidence which, as a whole, shows that the fact sought
to be proved is more probable than not. In other words, a preponderance of the evidence means such evidence
as, when considered and compared to the evidence opposed to it, has more convincing force, and produces in
your mind’s belief that what is sought to be proved is more likely true than not true. (O’Malley et al., 2006,
§104.01)
3
1. The use of the preponderance of evidence standard for civil trials is not universal. In civil or Roman law jurisdictions, for
instance, a higher standard of proof for civil trials is generally demanded, with some jurisdictions recognizing no official
distinction between the civil and criminal standards (see for instance Clermont and Sherwin, 2002). A comparison between civil
standards of proof in common law and Roman law traditions is beyond the scope of this paper, but I will briefly return to this
issue in n. 12.
2. In most Commonwealth countries, only two legal standards of proof are officially recognized—the preponderance of evidence
standard for civil trials and the beyond reasonable doubt standard for criminal trials (see for instance, Gabriel, 2013; Rejfek v
McElroy 112 CLR 517 [1965]; Re B (Children) [2008] UKHL 35). In the United States, however, there are further standards of
proof that are given official legal status; the ‘probable cause’ standard is taken to be weaker than preponderance of evidence,
while the ‘clear and convincing evidence’ standard—used in some civil trials—is taken to be intermediate in strength between
preponderance of evidence and beyond reasonable doubt (see Broun et al., 1984: §340 and, for instance, Cruzan vDirector of
Mississippi Department of Health 497 US 261 [1990]). In a civil case decided according to the higher clear and convincing
evidence standard, the plaintiff, much like the prosecution in a criminal trial, is required to offer much stronger evidence than
the defendant in order to prevail. The probabilistic interpretation of the preponderance of evidence standard can be presented as
part of a broader picture on which all legal standards of proof correspond to particular probability thresholds (such a picture is
set out, though not endorsed, in Laudan, 2006: 56 and Gardiner, 2018: section I; see also Schwartz and Sober, 2017: 623; United
States vFatico 458 F.Supp 388 [1978] at 403). This undeniably makes for a simple and cohesive overall interpretation—and
one on which it is easy to ensure that the various standards satisfy the required relations of comparative strength.
3. In their survey of pattern civil jury instructions across US jurisdictions, Schwartz and Sober found that the civil standard of
proof was explained in terms of a 50%probability threshold—using phrases such as ‘more probable than not’—in 21 of the 47
jurisdictions surveyed. In 17 jurisdictions, the standard was described using the more neutral terms ‘preponderance of the
evidence’ or ‘greater weight of evidence’. In the remaining nine jurisdictions, the pattern instructions included both char-
acterizations, or were otherwise deemed ‘ambiguous’ (see Schwartz and, Sober 2017: n. 86).
184 The International Journal of Evidence & Proof 25(3)

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