The values of prediction in criminal cases
| Published date | 01 April 2021 |
| Date | 01 April 2021 |
| DOI | 10.1177/13657127211002290 |
| Author | Hylke Jellema |
| Subject Matter | Articles |
Article
The values of prediction
in criminal cases
Hylke Jellema
University of Groningen, Groningen, Netherlands
Abstract
Like scientists, investigators and decision-makers in criminal cases both explain known evi-
dence and use the resulting explanations to make novel predictions. Philosophers of science
have made much of this distinction, arguing that hypotheses which lead to successful predic-
tions are—all else being equal—epistemically superior to those that merely explain known
data. Their ideas also offer important lessons for criminal evidence scholarship. This article
distinguishes three values of prediction over explaining known facts in criminal cases. First,
witnesses who predict are—all else being equal—more reliable than those who do not because
they are less likely to be biased or lying. Second, investigators who only explain known facts run
the risk of ‘fudging’ the scenarios that they formulate. Predictions can protect us against this
danger. Third, carefully constructed predictions may help investigators to avoid confirmation
bias. This article ends with a case study of the murder of Hae Min Lee.
Keywords
confirmation bias, evidence, legal proof, philosophy of science, prediction, predictivism
Introduction
Like scientists, investigators and decision-makers in criminal cases both explain known evidence and
use the resulting explanations to make new predictions. For instance, imagine that a detective suspects
someone of being the perpetrator of a criminal act because he was near the scene of the crime. Alter-
natively, imagine that this detective comes to suspect him for some other reason and only later finds out
that this person was near the crime scene. In both cases the detective ends up formulating the scenario
that this person was the perpetrator. Furthermore, in both cases she has at least one piece of evidence
supporting this scenario—namely that this person was near the crime scene. Yet this piece of evidence
comes to support the scenario in different ways. In the first case, the evidence was accommodated—the
detective formulated the scenario based on this known piece of evidence. In the second case, the
evidence was predicted—the detective did not use it in constructing the scenario.
Corresponding author:
Hylke Jellema, University of Groningen, Faculty of Law, Oude Kijk in ‘t Jatstraat 26 Groningen, 9700 AB Netherlands.
E-mail: h.jellema@rug.nl
The International Journalof
Evidence & Proof
2021, Vol. 25(2) 163–179
ªThe Author(s) 2021
Article reuse guidelines:
sagepub.com/journals-permissions
DOI: 10.1177/13657127211002290
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Philosophers of science have made much of the distinction between prediction and accommodation.
In science, successful predictions are often seen as one of the hallmarks of a good theory and scientific
theories that make no testable predictions are often seen as defective—even if they explain the known
data. Because of this, many philosophers of science argue for predictivism—the thesis that successfully
predicted facts provide stronger evidence for a theory than successfully explained known facts. In this
article I argue that the predictivist debate from the philosophy of science can teach us valuable lessons
about criminal evidence too.
In criminal law, predictions do not derive from scientific theories, but from scenarios—which are
accounts of what happened in a case. For instance, in a murder case a typically scenario details who
killed the victim, how they did so, and why they did it. Such scenarios both explain known evidence
and produce further evidence that we might expect to find. Though it may happen less than in science,
we also encounter predictivist intuitions regarding the predictions of scenarios. For instance, Joseph-
son (2000) claims that checking whether a crime scenario’s predictions are confirmed is one of the
most important criteria on the basis of which we should assess such scenarios. The necessity of
checking predictions is also repeatedly emphasised by van Koppen (2011: e.g. 76) —who mentions
their importance in science as an illustration of why they are important in criminal cases too. A more
explicit appeal to predictivism is made by Mackor (2017), who adopts a Lakatosian position on the
value of predictions. She draws an analogy between the role of predictions for assessing scientific
research programmes and their role in assessing scenario’s. However, though she briefly alludes to the
contemporary predictivist debate, she does not discuss the arguments from this debate in detail.
Finally, Tuzet (2019) does discuss one argument from the contemporary predictivist debate, namely
Peter Lipton’s fudging argument.
1
Based on this argument he suggests that predictivism also holds
with respect to legal evidence. Nonetheless, his discussion of this point is brief and in need of further
elaboration. So, at least some authors consider predictions to have a value above and beyond a scenario
merely accommodating the known facts. Nonetheless, we currently lack a systematic examination of
what this value might be.
The goal of this article is to address this gap. I examine several existing arguments about the
value of prediction developed by philosophers of science and show that analogous arguments can
be made with respect to criminal cases. In particular, this article develops three arguments for the
special value of predicted over accommodated criminal evidence. First, witnesses who predict
are—all else being equal—more reliable than those who do not because they are less likely to
be biased or lying. Second, investigators who only accommodate run the risk of ‘fudging’ the
scenarios that they formulate: they sacrifice the quality of a scenario to make it fit the facts.
Predictions can protect us against this danger. Third, carefully constructed predictions may help
investigators to avoid confirmation bias. In order to show how these arguments play out in real,
complex situations, I end this article with a case study of the murder of Hae Min Lee. This murder
was the subject of the popular 2014 true crime podcast Serial.
On predictions and evidential strength
This article examines various arguments for predictivism—the thesis that successful predictions yield
stronger evidence than successful accommodations. As a preliminary, let’s look at the notions of pre-
diction, accommodation and evidential strength.
1. I discuss this argument under ‘Fudged scenarios’.
164 The International Journal of Evidence & Proof 25(2)
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