Argumentation
DOI 10.1007/s10503-011-9257-0

Solving a Murder Case by Asking Critical Questions:
An Approach to Fact-Finding in Termsof Argumentation and Story Schemes
Floris Bex • Bart VerheijÓ Springer Science+Business Media B.V. 2011

Abstract In this paper, we look at reasoning with evidence and facts in criminalcases. We show how this reasoning may be analysed in a dialectical way by meansof critical questions that point to typical sources of doubt. We discuss criticalquestions about the evidential arguments adduced, about the narrative accounts ofthe facts considered, and about the way in which the arguments and narratives areconnected in an analysis. Our treatment shows how two different types of knowledge, represented as schemes, play a role in reasoning with evidence: argumentation
schemes and story schemes.
Keywords
Narrative

Argumentation schemes  Case-study  Evidence  Legal reasoning 

1 Introduction
In this paper, we propose critical questions for the process of proof, that is,reasoning about the facts and the evidence in criminal cases.1 This process involves
1

We use the term ‘‘fact’’ in its juridical sense, that is, descriptions of states or events the truth of which iscurrently unknown and has to be proven (cf. facta probanda or facts in issue, Anderson et al. 2005). With‘‘evidence’’ we mean the evidential data, the primary sources of evidence the existence of which cannot
be sensibly denied (e.g. witness statements made in court, forensic expert reports handed to the jury).
Evidence and facts should not be confused: the existence of the evidential data does not guarantee thetruth of the fact evidenced. For example, that there is a testimony by a witness who saw the suspect jump
F. Bex (&)
Argumentation Research Group, School of Computing, University of Dundee, Dundee, UK
e-mail: florisbex@computing.dundee.ac.uk
B. Verheij
Department of Artificial Intelligence, University of Groningen, Groningen, The Netherlands
e-mail: b.verheij@ai.rug.nl

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constructing, testing and justifying hypotheses about what (might have) happened ina case. The process is guided by the available evidence (e.g. witness statements,
tangible evidence such as a knife or blood) and by general knowledge (e.g.
generalizations such as ‘witnesses under oath usually speak the truth’ or scenariosthat express typical criminal behaviour).
In other work (Bex 2011; Bex et al. 2010), we have argued that both arguments
and stories (or narratives) are needed in order to do justice to all the relevant
reasoning mechanisms as they are recognised and used by decision makers andinvestigators. Stories—in the sense of coherent sequences of events—are needed toorganise the complex mass of facts in a case into one or more hypotheses about‘‘what happened’’ in the case (Pennington and Hastie 1993; Wagenaar et al. 1993;
Pardo and Allen 2007). Arguments consisting of (a chain of) defeasible inferences
based on evidence can then be used to support or attack the individual facts in thesehypothetical stories (Anderson et al. 2005; Bex et al. 2003; Walton 2002). We haveproposed a hybrid argumentative-narrative approach to reasoning in the process of
proof, in which arguments and narratives can be used in conjunction as well asinterchangeably. Thus, the decision about which facts to accept is based on theacceptability of the stories in light of the evidential arguments in the case.
Arguments in the process of proof will often be based on general knowledge
expressed as generalizations such as ‘expert statements may usually be believed’ or‘Analyses of DNA samples have probative value’. These generalizations can takethe form of the well-known argumentation schemes,2 general patterns of reasoningthat underlie an argument and that have associated critical questions that point totypical sources of doubt for such an argument. The acceptability of arguments in acase can then be critically analysed using these questions and possible counterarguments can be constructed on the basis of the (unsatisfactory) answers to thesequestions. Furthermore, argumentation schemes may point to missing parts of theargument. Thus, the argumentative part of the hybrid theory clearly falls within the
dialectical (critical rationalist) approach as discussed by, among others, vanEemeren and Grootendorst (1992, Chap. 2).
The stories that occur on the process of proof are based on general knowledge orschematic patterns, the so-called story schemes.3 For example, a story scheme for‘‘intentional actions’’ specifies a pattern of event types that a typical story aboutsome intentional action contains (e.g. motive—action—consequence) and a‘‘restaurant’’ scheme describes a pattern of events that a typical story about avisit to a restaurant contains (e.g. ordering—eating—paying). These story schemes
Footnote 1 continued
into a car does not guarantee that the suspect jumped into a car (the witness might lie or he might confuse
the suspect with someone else).
2

The concept of argumentation schemes was introduced by Perelman and Olbrechts-Tyteca (1971). See
also Garssen (2001), van Eemeren and Grootendorst (1992), Kienpointner (1992) and Walton et al.
(2008).

3

The idea of general patterns of (types of) events that underlie stories stems from literature theory (e.g.
Propp 1968) and has found applications in Cognitive Psychology and AI (Rumelhart 1975; Schank and
Abelson 1977; Schank 1986). We have previously addressed the role of story schemes in the process of
proof (Bex 2009; Bex and Verheij 2010; Bex 2011).

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can aid an analyst by, for example, serve a purpose as templates for possible
hypotheses about what happened in the case. However, they also serve a dialecticalrole: as with argumentation schemes, story schemes may point to missing parts of astory and one can ask critical questions associated with a story scheme (Bex et al.
2009).
In sum, in our approach both story schemes and argument schemes are used in adialectical way. For instance, when the prosecution claims that the suspect has
murdered the victim, without providing a motive, the mentioned story scheme forintentional action shows that the prosecution’s case can be improved by providing
the motive or explaining why it is missing. Similarly, when the prosecution argues
that the suspect was at the scene of the crime on the basis of an analysis of a DNA
sample, the defence can use an argumentation scheme for the use of a DNA sample
analysis to attack the prosecution’s argument, e.g. by trying to show that the sample
was contaminated.
In this paper, the dialectical value of stories and arguments is made explicit byproviding a list of critical questions. It will turn out that there are three types ofcritical questions for critically analysing a complex criminal case in a dialecticalway: (i) critical questions associated with the argumentation schemes, that can beused to analyse arguments based on evidence; (ii) critical questions associated withthe story schemes, with which the hypothetical stories about the facts may beanalysed; and (iii) critical questions for a hybrid argumentative-narrative caseanalysis, which may be used to analyse the case as-a-whole, that is, the combinationof stories and arguments supporting or attacking these stories.
We illustrate the role of the different critical questions with a case study, namely
the Dutch Nadia van der V. murder case.4 The case concerns the killing of student
Nadia. She has been killed in her home by several gunshots fired at her head andbody from close range. Her landlord, Pascal F., is regarded as the prime suspect. He
has been seen fleeing town in Nadia’s car and is not to be found until well into thenext year. When Pascal is finally apprehended, he is charged with murder and foundguilty by the lower courts as well as on appeal.
In our case study, we performed a post-trial analysis by looking at the verdicts in the
Nadia van der V. case.5 One of our main reasons for analysing these court verdicts wasthat we wanted to check whether they met the standards of a so-called explanatory
justification (Nijboer and Sennef 1999): a justification of a decision about the facts
which makes sense to not just the reasoner but also to third parties. These types ofjustifications for verdicts have become important in the current Dutch legal practice,as due to a number of highly publicised miscarriages of justice the political and publicpressure on judges and the way they arrive at their decisions has increased.
In our analysis of the case, we drew up a list of critical questions. These criticalquestions were then systematically applied to the case as presented in the court4

We started our analysis of this case in (Bex and Verheij 2009; Bex and Verheij 2011a), of which thepresent paper is an extension.

5

In the Netherlands the judges are required to provide a written verdict in which their considerations are
summarized. Many of these verdicts are available to the public on http://www.rechtspraak.nl. The verdicts in the Nadia van der V. case are available (in Dutch): LJN AO3150 (court of Utrecht) and LJN
AT5190 (court of appeal Arnhem).

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verdicts and for each question it was determined whether and how it had beenanswered. Our findings are presented in Sect. 4. First, we review the use of thehybrid approach in the process of proof in a semi-formal way (for further formal
detail about the hybrid theory, see Bex et al. 2010; Bex 2011) and we discuss
argumentation schemes and story schemes as they are used in the process of proof is
Sects. 2 and 3, respectively. Section 5 concludes the paper and proposes someresearch questions for the future.

2 A Hybrid Argumentative-Narrative Theory
In the research on the process of proof, essentially two trends can be distinguished.
The first method for analysing evidence focuses on structured arguments.6 In thisapproach, arguments are constructed by performing consecutive reasoning steps,
starting with one or more items of evidence and reasoning towards a conclusion,usually a fact that has to be proven. The second method for analysing evidence
mainly uses stories to structure and analyse the available evidence.7 This approach
involves constructing coherent accounts of the facts about ‘‘what happened’’ in thecase that explain the evidence.
The distinction between purely argument-based and story-based approaches as
set out in the above paragraph is a slightly artificial one: the concepts of argument
and story play an (implicit) role in research on either side of the spectrum. For
example, Wigmore and Anderson and colleagues take a primarily argumentative
perspective, but do discuss stories (though primarily as rhetorical devices), while
several of Wagenaar and colleagues’ central claims in their anchored narratives
theory have a more argumentative than story-based flavour (especially the role ofgeneralizations and exceptions to these generalisations).8
In addition to differing central concepts (stories and arguments), another aspectthat is seemingly different between the argument-based and story-based approach isthat the argument-based approach is clearly normative (i.e. it tells us how we should
rationally analyse reasoning about evidence and facts in the process of proof) whilst
the story-based approach is originally based on more descriptive work (i.e. it tells us
how people analyse the evidence and the facts in the process of proof).9 However, in
6This approach has its roots in Wigmore’s (1931) evidence charts and has been further developed by‘‘New Evidence Theorists’’ such as Anderson et al. (2005). Similar argument structures have been
discussed by, among others, Freeman (1991), Reed et al. (2007) and Verheij (2005b). Bex et al. (2003)
have further discussed the link between Wigmore’s graphs and such argument structures.

7This explanatory story-based approach, the main proponents of which are Wagenaar et al. (1993) andPardo and Allen (2007), is based on work from cognitive and legal psychology (Bennett and Feldman
1981; Pennington and Hastie 1993).

8

Argumentative analyses of the anchored narratives theory by Wagenaar, Crombag and Van Koppen
have been given by Verheij (2000), Bex et al. (2006) and Verheij and Bex (2009).

9

Anderson et al.’s work, for example, is firmly based on what is called the Rationalist Tradition(Anderson et al. 2005, pp. 78–86), which argues that it is necessary to rationally reason with the evidence
in order to establish whether or not our belief in the facts is justified. Conversely, Bennett and Feldman’s(1981) and Pennington and Hastie’s (1993) work was also meant as a descriptive theory of how people
reason with masses of evidence in legal cases.

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other work Twining (1999) has cautiously agreed that stories are also necessary forrational decision-making (that is, they serve more than a rhetorical function) whilst
Wagenaar et al. (1993) and Pardo and Allen (2007) add a specific normative
component to reasoning with stories, particularly in the way they define the processof an analysis of the evidence and the burden of proof for explanatory stories,
respectively.
The somewhat blurry boundaries between the two trends in the literature has led
us to believe that there is a need for an integrated, hybrid approach of stories andarguments. Hence, Bex and colleagues (Bex et al. 2010; Bex 2011) proposed a
hybrid argumentative-narrative theory for Inference to the Best Explanation (IBE).
The idea behind the hybrid theory was that both arguments and stories play a role indialectical and critical decision-making about the facts.10 In developing this theory,
we take sides with van Eemeren and Grootendorst’s11 idea that normative
idealisation and empirical description should be properly combined in a comprehensive theory of argumentation. Hence, the theory should be based on forms of
reasoning that are natural to us and that we actually use, whilst at the same time thetheory should impose rational constraints on this reasoning so that mistakes can be
avoided.
The basic idea of this hybrid theory is that the observed facts to be explained, theexplananda, are explained by different stories, alternative explanations of what
happened in the case. These stories can then be reasoned about using arguments. For
example, arguments can be used to support the story with evidence or to reason
about the plausibility of the stories. Ultimately, the explanations in a case should becompared and the best one should be chosen. Below we will briefly review the useof arguments, stories and their combination in light of the process of proof. In Sect.
2.2, we will raise the fundamental issue why to some extent arguments and stories
seem to be a kind of communicating vessels.
2.1 Arguments and Stories in the Process of Proof
The process of proof usually starts when some initial evidence is found that involves
the possibility that a crime has been committed. On the basis of this preliminary
evidence one can formulate one or more explananda, that is, observed facts thathave to be explained.12 In the Nadia case the police found Nadia’s body; hence, themost important explanandum in the case was the fact that Nadia died. On the basisof this explanandum, some hypotheses about what might have happened to Nadia
will have to be imagined. This may be done by performing abductive inference.13
10

The rhetorical role of both arguments and stories, while interesting, has not been explored in the workon the hybrid theory.
11

See van Eemeren (1994) for a concise introduction to this view.

12

Often, new explananda appear during the investigation or treatment of a case. For example, once a
possible suspect has been found a new explanandum could be ‘‘why was this man acting suspiciously near
the crime scene?’’13
Josephson (2002) discusses abductive reasoning in the context of reasoning with narratives andcriminal evidence. Walton (2001) provides a more general account, contrasting abductive reasoning with
presumptive and plausible reasoning.

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Fig. 1 Alternative stories which explain an explanandum

This type of inference involves ‘‘guessing’’ new hypotheses that explain someobserved data: if we have a general rule ‘c explains e’14 and we observe e, we areallowed to infer c as a possible hypothetical explanation of the effect e. This
explanation c which is used to explain the effect can be a single state or event, but it
can also be a story. The usual definition of a story in, for example, literature theory(e.g. Toolan 2001) is that it is a chronological and coherent sequence of events
experienced by actors. We will return to this issue of coherence below.
Taken by itself, abductive reasoning can be considered to be the fallacy ofaffirming the consequent. However, the inferential value of abductive reasoning
becomes apparent in the broader context of IBE, where not just a single hypotheticalstory but also alternative scenarios are considered and the best one is chosen. In
Fig. 1, hypothetical stories in the Nadia case are visualised; the open-headed arrows
in this figure represent explanatory relations.
Given some hypothetical stories that explain the explananda, we have to find thebest explanation among the various alternatives. An important criterion when
judging how good a particular story is, is the story’s evidential support, the extent towhich the evidential data in the case supports a story. In the hybrid theory, supporting
stories is done by constructing arguments, starting with one or more items ofevidence and reasoning towards a conclusion, an element in the story (i.e. a state or
event or an explanatory link between events). Associated with the reasoning steps inthese arguments are generalizations that justify the inferences (cf. Toulmin’s 1958
warrants and the aforementioned argumentation schemes). Take the following
example from the Nadia case (Fig. 2): a witness testified that ‘a man who looked like
Pascal was in the car’. This statement, together with the generalization that‘witnesses usually speak the truth’ allows us to infer that ‘a man who looked like
Pascal was in the car’. This conclusion can then be combined with other information
to infer that it was indeed Pascal who was in the car. Thus, we get the argument tree
or diagram (cf. Wigmore 1931; Freeman 1991; Reed et al. 2007; Verheij 2005b)
pictured in Fig. 2, which supports story 1 from Fig. 1.
The argument in Fig. 2 uses various generalizations (rendered in the roundedboxes) to warrant the inferences. In addition to generalizations which are often used
14

Often, c explains e because c is a cause of e and in our other work we mostly model explanation using
causal links. However, in order to sidestep the often difficult and subtle discussions about causality, here
we simply talk about explanatory relations. This also allows, for example, teleological or intentional
explanations (see also Bex et al. 2009; and Bex 2011, pp. 24–31).

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Fig. 2 An evidential argument

in all criminal cases, such as the generalization that witnesses usually speak thetruth, more (case-) specific generalizations are also used as inference licences. For
example, the top inference is warranted by the generalization ‘if person x was in a
car at some time and someone looking like x has been seen in that car at time t, thenit is likely that the person in the car at time t was x’.
Thus, in the hybrid approach, stories can be evidentially supported by arguments.
Argumentation is inherently dialectical: not only evidence supporting a conclusion
but also evidence against it should be considered and sources of doubt in anargument should be actively challenged by giving counterarguments that attack theargument (e.g. the credibility of witness Bob can be questioned). When such a
counterargument is strong enough, the evidence no longer supports the story as thechain of reasoning from the evidence to the element of the story is effectively
broken. Furthermore, arguments can also be used to contradict stories: for example,
an argument based on Pascal’s statement that he did not kill Nadia contradicts story
1 from Fig. 1.
The choice between alternative stories depends not only on the extent to which
they conform to the evidence but also on the stories’ coherence, that is, whether thestory conforms to our world knowledge.15 Following (Bex 2011), we say that a story
is coherent if it is consistent, if it is complete (i.e. the story completes a plausible
story scheme, see Sect. 3.2) and if the individual explanatory relations are plausible.
For example, a story is less coherent if it is not consistent (e.g. the suspect was at
two places at once), if there are relevant parts missing (e.g. no motive is given for asuicide or in a case of theft it is not made explicit what was actually stolen) or if thestory is based on implausible causal information (e.g. shooting someone with a toy
15

Pennington and Hastie (1993) say that a story is coherent if it is consistent and it follows a generalmotive—goal—action—consequence sequence (see Sect. 3.2) and any individual causal links in the story
are plausible. In Thagard (2004) coherence depends on the numerical strength of the explanatory relations
between events in the story, which is in turn determined by formal coherence principles.

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Fig. 3 Reasoning about a story using arguments

gun causes that person to die). The hybrid approach makes it possible to reason
about the coherence of a story in a dialectical way: arguments can be given to
support or attack explanatory or causal relations in a story. For instance, by arguingthat ‘normally, people do not shoot other people because of a simple disagreement’,
we attack story 1 in Fig. 1, where the disagreement is given as a motive for Pascal
shooting Nadia.
Figure 3 visualises how the facts are organised in a story that explains the
explanandum (i.e. ‘‘Nadia died’’, which is itself part of the story) and how theevidence is connected to these facts using arguments. As in Figs. 1 and 2, the arrows
denote explanatory relations and the arrows denote inferential relations. The
argument from Fig. 2 supports that Pascal fled in Nadia’s car and an argument basedon a forensic report supports the fact that Nadia’s death was caused by a gunshot(though not necessarily Pascal firing this shot). The arrow stands for an attack or
conflict relation: recall that before we gave the example of Pascal’s denial attacking
the main action in story 1 from Fig. 1.
To summarise, both arguments and stories play important roles in reasoning
about the facts and the evidence. Stories are needed as hypothetical scenarios and to
fill gaps in the evidence (see Sect. 4.2): whilst abductive and causal reasoning canalso be modelled using arguments,16 it is arguably more natural to model them as
stories (Prakken 2011) because this also allows for timelines and more ‘‘holistic’’rendition of stories.17 Furthermore, such stories provide an overview and make thecase-as-a-whole understandable.18 If we are to provide useable method foranalyzing masses of evidence, we should adhere to the empirical reality, lest we
restrict ourselves to what van Eemeren (1994) calls the ‘‘world-independent
regimentation’’ of logic. Finally, it can be argued that standards of proof,

16

See e.g. Walton et al. (2008, Chap. 5).

17

As is argued by Schank and Abelson (1977) and Schank (1986), the knowledge that is used when
thinking about patterns of action often does not have the form of individual causal or explanatory rules
but is more naturally thought of as a collection of coherent and generalized events or event types, seeSect. 3.2.

18

Experiments by Pennington and Hastie (1993) have shown that stories that explain the facts are closest
to how legal decision makers actually think about a case and Wagenaar et al. (1993) hence argue thatstories are the only viable way to argue with complex masses of evidence.

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particularly that of ‘‘beyond a reasonable doubt’’ are easier modelled using
explanatory stories than arguments.19
A purely story-based approach, however, while it correctly describes people’s
reasoning with a mass of evidence, is not enough. Even if used rationally and in adialectical way (i.e. by explaining the evidence and providing alternative stories),
stories are still powerful rhetorical vessels that can be used to convince in a ‘‘nonrational’’ way.20 Hence, stories must be critically analysed.21 A good way to analyseboth the connection between the stories and the evidence and the commonsense
knowledge underlying the story is to use arguments. These arguments can be used in
the analysis of the credibility of individual pieces of evidence and their relevancefor the stories about the facts. Furthermore, using arguments we can not only argue
with stories, but also about the coherence of stories. Thus, the hybrid approachdraws from the extensive philosophical tradition in argumentation to enrich themore psychologically oriented, story-centred approaches.
2.2 Arguments and Stories as Communicating Vessels
In our proposal for the analysis of reasoning about the facts in a criminal case wehave combined stories and arguments so as to have a flexible and broad set ofanalysis tools. Here, it must be remarked that in our hybrid theory, we use specific,‘‘narrow’’ definitions of argument and story. According to these narrow definitions,an argument is a tree-like structure in which one or more premises support a single
conclusion through one or more consecutive inference steps, whilst a story is acoherent sequence of events in chronological order. Thus, arguments and stories are
distinct structures.
However, if a more broad definition of the term argument is followed, this
distinction fades. For example, if we say that an argument is ‘‘any reason given forsome conclusion’’, we could say that, for example, story 1 in Fig. 3 is an argumentfor Pascal’s guilt: the coherent set of facts provides a reason for us to believe that
Pascal is guilty.22 Thus, we do not need stories; instead, we can analyse a case using
just arguments (in the broad sense) that have sets of events as premises. It can also
be claimed that a causal or explanatory sequence is an argument (in the broad sense)
for the facts to be explained: thus, the story in Fig. 3 is an argument based on thecausal argument scheme with as its conclusion ‘‘Nadia died’’. Even if we accept theterminological convention that any sequence of events is called a story, it is still
possible to analyse the facts of the case without utilising these sequences and only
using arguments (in the narrow sense): as, for example, Wigmore (1931) and19

See Bex and Walton (2010), Pardo and Allen (2007), who have argued that reasoning in trials involves
comparing stories about the facts.

20

Twining (1999) and Anderson et al. (2005) argue that stories are ‘‘dangerous’’ because they can, forinstance, be based on false generalizations, and Wagenaar et al. (1993) argue that we should be careful
not to let a ‘‘good’’ story push away a ‘‘true’’ story.

21

This observation was already made by Pennington and Hastie (1993) and Wagenaar et al. (1993), who
say that a story must explain the evidence and that it must be anchored in safe commonsense knowledge.

22
See (Bex and Verheij 2011b) for a further discussion on how sets of facts can be used as reasons forlegal conclusions.

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Fig. 4 Stories and arguments as communicating vessels

Anderson et al. (2005) have shown, complex argument trees from the evidence tothe facts may be constructed and thus all the individual facts can be analysed.
Similarly, it is possible to incorporate the evidence itself in the story: the fact thatsomeone who looked like Pascal was in Nadia’s car (and the fact that a police
officer asked Bob what he saw) causes Bob to testify that ‘‘someone who looked
like Pascal was in the car’’). Here, the evidence is simply another event in the story
which is explained by other events.23 Stories are not supported by evidence; rather,
the story that explains the most evidence is considered to be the best.
These remarks suggest that to some extent the roles of stories and arguments inan analysis can be exchanged. Consider, as an example, Fig. 4. In this example, thesame piece of evidential data is used in two different ways. On the left side, thesuccessful scent test is used to infer that Pascal was in Nadia’s car (which ultimately
supports the fact that it was Pascal who murdered Nadia). The inference is attacked
by an argument that the police tampered with the evidence. On the right side, thestory that it was Pascal who murdered Nadia is used to causally explain the result of
the scent test. The counterargument is here modelled as an alternative explanation: astory that the police tampered with the evidence also explains the result of the test.
The situation in Fig. 4 shows that, in a purely argumentative approach,alternative interpretations of the evidence lead to counterarguments and in a purely
narrative approach, such alternative interpretation lead to different explanatory
stories. So it would seem that in the hybrid approach, an alternative story can also be
expressed as a counterargument. This specifically occurs when the stories actively
contradict each other. For instance, in Fig. 1, the ‘‘suicide’’ claim is raised as analternative hypothesis, an alternative story. However, from the claim that ‘‘Nadia
shot herself’’, we could argumentatively infer the conclusion that ‘‘Pascal did notshoot Nadia’’, which is a counterargument to the claim in story 1, that Pascal shot
Nadia (cf. Fig. 3, Pascal’s statement).
Since it is possible to emphasize either argument-oriented elements or storyoriented elements in a case analysis, one could say that arguments and stories
behave as ‘‘communicating vessels’’: a change in an argument-oriented version of acase analysis requires a matching change in a story-oriented analysis. As aconsequence of this ‘‘communicating vessels’’ property it is possible to choose whatworks best when performing an analysis: some cases or aspects of a case will more
23

This is the case in, for example, Pennington and Hastie’s (1993), Josephson’s (2002) and Thagard’s(2004) approaches.

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conveniently be modelled in terms of arguments, others in terms of stories. For
example, if the decision whether the suspect is guilty or not hinges on a single fact(e.g. whether the suspect was at a particular location at a particular time), alternative
stories are less important and the main analytical technique is to carefully consider
all the arguments for and against this fact. In other cases, certain facts might notnecessarily be justified because they are supported by strong evidence but rather
because they are part of the most coherent story. Take, for instance, a case withmultiple contradicting claims based on different testimonies. Simply considering
these claims as counter-arguments to each other does not tell us which one, if any, istrue. Rather, we should look which claim is part of the most coherent story that is
supported by the most additional evidence, that is, which claim is compatible withthe totality of the evidence.
We believe that the fact that arguments and stories to a certain extent behave as‘‘communicating vessels’’ indicates that there is room for a deeper understanding of
the relation between arguments and stories in reasoning about evidence, in such a
way that they are treated in a genuinely integrated way, instead of in the hybrid way
proposed here. Both similarities and differences should be more succinctly
emphasized in such an integrated approach. A requirement of an integrated
approach would be that it explains how and to what extent argumentative andnarrative elements of a case analysis can be exchanged, and when their differences
make this impossible. Furthermore, whether there are principles or heuristics tochoose between the different analytical tools is as yet an open question.

3 Argument and Story Schemes: The Knowledge Involved in the Processof Fact Finding
Evidence is the pivotal source of knowledge in evidential reasoning; the knowledge
gained from sources of evidence provides the case-specific ‘‘ground’’ on which allother reasoning about a case can be built (Fig. 3). However, evidential reasoning
also involves a large amount of knowledge about the world we live in. Thisknowledge is not based on direct evidence, but rather it is stored in what is
metaphorically called a stock of knowledge, a repository of general knowledge
about the world that is ‘‘stocked’’ in the reasoner’s mind (Cohen 1977). Parts of thisknowledge are commonsense (‘‘Murders normally involve a murder weapon’’),others require specific expertise (such as knowledge about the justificatory force of aforensic report, e.g. about a DNA match).
Our knowledge of the world allows us to assume or infer new information in a
way that is as reliable as is needed in the context. This type of knowledge, whilst
often accepted in a wide community, has varying degrees of reliability and for every
general scenario or generalization, there is at least one example of a situation inwhich it does not hold. The reliability of the knowledge we use depends on context.
For instance, in the beginning of the investigative phase, it may be useful to accept
some slightly implausible hypothetical scenarios and generalizations in order not toconstrain the investigation too much by setting high standards. Later on, in theactual decision-making process, more reliable knowledge corresponding to a stricter

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burden of proof (‘beyond a reasonable doubt’ as opposed to ‘possibly’) will be used.
As such, the use of our knowledge can have exceptions, its use involves the risk ofgetting it wrong and depends on context.
In the hybrid approach, knowledge about the world is used in two pivotal ways.
First, good and effective reasoning with evidence requires knowledge of pragmatic(not necessarily formal) rules of inference, generalizations which warrant inferencesfrom premises to conclusions. Second, knowledge of relevant scenarios or clustersof events is needed. Generalizations and scenarios can be seen as argumentation
schemes and story schemes, respectively, schemes that encode general patterns ofreasoning and knowledge. For example, a witness testimony argumentation scheme
is a general scheme for particular arguments based on witness statements. Similarly,
a murder story scheme is a general scheme for particular murder stories. In thissection the two types of schemes will be discussed.
3.1 Argumentation Schemes
The first kind of knowledge about the world that is needed in our hybrid approach toreasoning with evidence concerns the inference warrants underlying the reasoning
steps from evidence to some conclusion. In the research on argumentation theory,these are often referred to as argumentation schemes (Walton 1996; Walton et al.
2008). Argumentation schemes can be thought of as a semi-formal generalization of
the rules of inference found in formal logic (cf. Bex et al. 2003; Verheij 2003).24
They are closely related to Toulmin’s notion of warrants.
Argumentation schemes can be abstract or specific. For example, the standard
Modus Ponens inference rule can be seen as an abstract argumentation scheme. An
example of a more specific argumentation scheme is that for Argument fromWitness Testimony (Bex et al. 2003):
Witness w asserts that p is true (false).
Therefore, p may plausibly be taken to be true (false).
This scheme is essentially a conditional version of the generalization ‘witnesses
usually speak the truth’ from Fig. 2 (see Verheij 2005a for how generalizations canbe rewritten as a conditional scheme). Because argumentation schemes range fromabstract to specific, we can envisage hierarchies of schemes ranging from abstract,
domain independent rules (Modus Ponens) to more domain-specific and contextual
schemes (Witness Testimony, Expert Testimony), where some specific schemes are
instances of abstract schemes. For example, Witness Testimony and Expert
Testimony schemes are instances of the general Position to Know scheme (Walton
et al. 2008). Sub-schemes of the Witness Testimony scheme are, for example,
schemes for specific ‘‘types’’ of witnesses, such as witnesses under oath or witnesses
in a particular legal system.
24
In Walton’s treatment, argumentation schemes do not only occur as generalized rules of inference, butalso as (generalizable) small derivations or pieces of dialogue (Verheij 2003). Cf. also Prakken (2010)
who argues that some argumentation schemes are compressions of more complex types of defeasible
reasoning and Verheij (2009), who shows how argumentation schemes have been incorporated into moreformal models of argumentation.

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Argumentation schemes may come from a number of sources such as, forexample, logic or epistemology (e.g. Pollock’s 1987 rules for reasoning fromperception or memory).25 They represent stereotypical ways of reasoning about
which there is a consensus, at least in the relevant (philosophical) community. The
law may also point us to oft-used patterns in our reasoning: for example, in Dutch
law witness testimonies are explicitly stated as a species of evidence on the groundsof which a judge can form his decision (articles 339 and 342 Dutch Code of
Criminal Procedure). This means that it is highly unlikely that the legislator
believed the witness testimony generalization to be false by default.
One of the main points of looking for stereotypical patterns of reasoning is thatfor each scheme some typical sources of doubt can be given. For argumentation
schemes, these sources of doubt are expressed as critical questions. For the Witness
Testimony scheme, we can ask, for example, ‘Does witness w accurately rememberp?’ and ‘Does w have a reason for lying about p?’ Critical questions show where
possible weak spots in an argument from Witness Testimony might be, and they canbe used to analyse such an argument.
3.2 Story Schemes
In the 1970s, the fields of cognitive science and artificial intelligence took an active
interest in stories. This research mainly focused on developing formal grammars fordescribing the structure of a typical story (e.g. Rumelhart 1975). These story
grammars divide stories into episodes, which consist of a beginning, development
and consequences. In later research, in particular Schank and Abelson (1977), more
specific story-patterns called scripts or explanation patterns are given, which help instory understanding. For example, the ‘restaurant-script’, which contains information about the standard sequence(s) of events that take place when somebody goes todine in a restaurant, helps us understand a simple story about someone who goes todine in a restaurant because it fills the gaps, the events which are not explicitly
mentioned in the story (e.g. the person reading the menu). Scripts and explanation
patterns can also be used to explain an event (Schank 1986), as they connect theevent with an explanation that has been used to explain the event before.
Episodes, scripts and explanation patterns can be seen as instances of somethingwhich we call story schemes, general patterns of (types of) events that can serve as a
background to particular stories. Like argumentation schemes, story schemes range
from abstract to specific. For example, a scheme beginning—middle—end is a very
abstract scheme for stories. Pennington and Hastie’s (1993) episode scheme forintentional actions, a pattern of the form motive—goal—action—consequences, ismore specific. Even more specific schemes mention not only a sequence of events,
but also other information important in a story of that particular type. Take, forexample, the story scheme for ‘murder’:1.
2.

Anomaly that the scheme explains: person y is dead.
Central action of the scheme: person x kills person y.

25
See Hitchcock (2010) for an exposition of how logicians or epistemologists might go about
constructing (new) argumentation schemes.

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F. Bex, B. Verheij

3.
4.
5.

Other relevant information: the motive m, the time of the killing t, the place of
the killing p, the weapon w.
Pattern of actions: person x has a motive m to kill person y—person x kills
person y (at time t) (at place p) (with weapon w)—person y is dead.
More specific kinds of murder: assassination (e.g. liquidation), felony murder(e.g. robbery murder), killing of one’s spouse.

In addition to a pattern of actions, this scheme also contains other information,such as what the central action is and which other, more specific schemes might beapplicable. The story about Nadia fits this scheme with, for example, motive
m being the disagreement and the weapon w a gun.
Like argumentation schemes, story schemes are hierarchical in that specificschemes can be seen as instances of abstract schemes. For example, a murder is an
instance of an intentional action (where, e.g. the action is person x kills person y),which is in turn an instance of the standard beginning—middle—end scheme forstories. Story schemes are also hierarchical in that an element of one scheme mayitself be comprised of a scheme. For example, the motive of a murder may be
another murder: x’s motive for killing y may be that y killed x’s brother.
An argumentation scheme denotes an inferential relation between propositionsand (the sequence of events in) a story scheme denotes coherence relations between
events or event types. Hence, a particular story and its corresponding scheme can berendered in a way similar to a particular argument and its corresponding scheme(s).
As an example, see Fig. 5, in which the explanatory relations from the murder story
scheme are expressed in natural language in the same way as the (inferential)
relation expressed by the Witness Testimony argumentation scheme in the argumentin Fig. 2 is expressed in natural language.
Story schemes are important in reasoning about the facts because they serve as
possible templates for the hypotheses in IBE. Schank (1986) argues that there arethree ways of performing abductive reasoning when we want to explain some
explananda. The first way is to look at specific similar cases; for example, if wewant to explain why Pascal fled in Nadia’s car we can look at other situations inwhich Pascal behaved in a similar way. This way of reasoning uses case-specificscenarios and is hence similar to argumentative reasoning with case-specificgeneralizations (cf. the top inference in Fig. 2). The second way to explain an
explanandum is to find an explanation for an event in the form of an existing story
scheme. For example, faced with Nadia’s body we invoke the murder scheme. The
third, and arguably the hardest way to explain an event happens when there is no
particular story scheme that seems to fit the current case; we then have to build aFig. 5 A story with causal relations expressed as generalizations

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new scenario from scratch. Very often, however, there will be some kind of story
scheme that can be recalled from memory. In our informal contacts with the Dutch
police force, they repeatedly insisted that when faced with some initial evidence,
they have a range of standard scenarios (i.e. story schemes) they turn to.
In addition to aiding abductive inference, story schemes can also be used to
critically analyse existing stories and, in particular, the coherence of stories. For
example, if a story does not fit a particular scheme because some of the elements ofthe scheme are not in the story (for example, no mention is made of the motive in amurder story or the causal link between the murderous action and the victim’s death
is not made clear), the story’s coherence diminishes. Additionally, the criticalquestions associated with the story scheme may be asked. Bex et al. (2009) give alist of critical questions for the intentional action scheme, a few of which wemention here.
1.
2.
3.
4.

Can there be another motivation which is a deterrent for doing the action?
Can the action be induced by some other motive?
Is the motive a legitimate motive for the action?
Can the action have the stated consequences?

For example, for the story in Fig. 3 we need to determine whether Pascal might
have some other motivation that deterred him from shooting Nadia (e.g. themotivation not to get into trouble with the police), whether Pascal could have hadsome other motive (e.g. self-defence), whether a disagreement is a valid motive forshooting Nadia and whether shooting Nadia might have killed her.
Story schemes have been examined in the field of Case Based Reasoning (e.g.
Schank and Abelson 1977; Schank 1986). Pennington and Hastie (1993) and
Wagenaar et al. (1993) both use the relatively simple intentional action scheme andthey do not further examine specific schemes in evidential reasoning. There is a
recent rise in attention for the computational modelling of the role of narrative incognition (Finlayson et al. 2010). Our use of story schemes in argumentation is, as
far as we are aware, quite novel. There have been attempts at systematising story
schemes, mostly with regards to fictional tales (e.g. Propp’s 1968 systematisation of
the structure of Russian folk tales). Exactly which schemes are often used in a(criminal) legal context and which critical questions can be associated with theseschemes remains an open question.

4 Critical Questions for the Hybrid Theory: The Nadia van der V. CaseOn the 1st of October 2002, the police find student Nadia van der V. in her home,dead. She has been killed by several gunshots fired at her head and body from close
range. Her landlord, Pascal F., is regarded as the prime suspect. He has been seen
fleeing town in Nadia’s car and is not to be found until well into the next year. When
Pascal is finally apprehended, he is charged with murder and found guilty by thelower courts as well as on appeal. Looking at the verdicts of the case, it is not hard
to see why the judges chose to believe the prosecution’s story: Pascal is an exsoldier who is known for his volatile behaviour and there are numerous witnesses

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who testify about Pascal’s flight from the police on the day of the murder. The
defence, on the other hand, is less fortunate: the only alibi Pascal provides is a vague
story about him being abducted and taken to Poland by people he did not know;later, Pascal even admits he fled from the police because he was afraid he would be‘‘framed’’.
Even though at first glance the prosecution’s story is more coherent, and thus
more plausible, we must be careful not to accept it too readily, as psychologicalresearch has shown (Bennett and Feldman 1981; Pennington and Hastie 1993) that agood story need not necessarily be a true story. Our hybrid argumentative-narrative
approach gives rise to a number of critical questions that can be asked to unearth
sources of doubt in a total case (i.e. the combination of arguments, stories andevidence) in the same way as critical questions for argumentation schemes point tosources of doubt regarding a single inference and critical questions for story
schemes point to sources of doubt in a particular story. These critical questions canessentially be asked during any stage of the process of proof (i.e. pre-trial, during
trial and post-trial). As was already mentioned, we performed a post-trial analysis
by looking at the publicly available verdicts in the Nadia van der V. case.
4.1 Insufficiently Specific Accounts of the Facts
The starting point of a well-supported opinion about the facts is a concrete story
about what happened, that is, a sufficiently specific and coherent account of what(might have) happened in a criminal case. By presenting the story separately fromany arguments about its coherence and the evidence, the coherence of the story canbe best appreciated and investigated. In a sense, one can say that this story is theconclusion of the total argument about the case (here, we use the term ‘‘argument’’in the broad sense, cf. Sect. 2.2). Which stories can be the conclusion of a legal
verdict is often restricted by formal constraints; for instance, in the Netherlands thefactual account of a conviction should match the indictment presented by theprosecution. Here we abstract from such constraints.26
Thus, the first critical question for rational fact finding can be phrased as follows.
(1)

Are the facts of the case made sufficiently explicit in a story?
A case should contain a clearly phrased, sufficiently specified and coherent
story detailing ‘‘what happened’’. Such a story is the issue to be investigated ordebated, and will—if successfully argued for—be the conclusion of the case.

In the Nadia case, a story can be reconstructed on the basis of the verdicts of thecourts.
Nadia, a student living in Utrecht and her landlord, Pascal, had had adisagreement about a washing machine. On the 1st of October, Pascal lost hishead and decided to kill Nadia. At 8:30 in the morning, he called his work toreport in sick and grabbed a small machine gun he had in his room. Nadia wasdoing the laundry while calling a friend using her hands-free earpiece; the two
26
In Bex and Verheij (2011b), we further explain the link between the factual and the legal aspects of a
case.

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other tenants had left earlier that morning. Around 8:53, Pascal confronted
Nadia in the hallway. At first, Nadia greeted him but quickly she saw that he
was up to no good and started screaming. At that point, Nadia’s telephone
conversation with her friend was interrupted. Pascal shot Nadia twice, whichcaused her to collapse. He then dragged her to the kitchen, where he killed her
by shooting her through the head three times at close range. Pascal thendragged her body to his part of the house and closed this part off.
At approximately 9 o’ clock, Pascal left the house and drove towards thenearest access to the motorway in Nadia’s car. At 9:10, he suspected someone
deliberately tried to cut him off on the motorway’s access ramp. He steered thecar off the ramp, got out and left it. Pascal was afraid the police was looking
for him and he tried hiding for a helicopter in the nearby woods. Later that day(around 18:15), Nadia’s body was found by the police, which had been alerted
by the other tenants who had returned home. Pascal visited his parental homeon the 2nd of October, where he briefly spoke to his father. Pascal then left for
Poland where he stayed until the 29th of January. When he returned, he wasapprehended by the police and put into custody.
This story, which was taken from the courts’ verdicts with a minimal amount ofinterpretation on our part, provides a clear, specific and coherent account of what
happened; the first critical question provides no problems.
4.2 Insufficient Support of the Facts
One’s belief in the truth of a story about what happened must be supported byevidence. A key step is the identification of the evidential support that can be given
for the elements of a story, that is, identifying the sources of evidence that support
the story. In general, not all elements of a story can be supported by evidence. This
does not need to be a problem, and is in fact unavoidable as certain story elements
must by their nature be indirectly justified. When an element of a story is notsupported by a piece of evidence (in a given argument), we speak of an evidential
gap (Bex et al. 2010; Bex 2011). A typical example of an evidential gap occurs
when proving criminal intent. Sometimes criminal intent can be supported directlyby, for example, the confession of the suspect. But very often the criminal intent of
the suspect is simply assumed; this assumption is justified because it fits a coherent
story about the facts that is supported by additional evidence. For example, when thesuspect is caught red-handed while leaving the house through a broken window witha backpack filled with a crowbar and the house owner’s digital camera, the suspect’s
criminal intent can be safely assumed.
The existence of evidential gaps, here conceived of as parts of a story for which
no direct evidence27 is available, is one reason why a mixed-argumentative narrative
perspective can be useful. The analytical argumentative perspective makes the27

There is theoretical discussion about the nature and existence of direct evidence, see for instanceAnderson et al. (2005), pp. 62–63. For our purposes, it suffices to note that we consider an event to be
directly supported when there is a direct, argumentative (evidential) chain of reasoning from evidence tothe event.

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evidential gaps visible, the narrative perspective shows why the evidential gaps canstill be believed in conjunction with other facts. In general, it is a matter of good
judgment which elements of a story must be directly supported by evidence andwhich can be assumed in conjunction with the other facts. This depends in part on
the quality of the evidence (a story supported by only weak evidence can become
stronger by providing evidence for more facts), but also on the nature of the crime
itself. For instance, in a murder case, a case without a murder weapon is in bad
shape, let alone when the body has not been found. We will call a component of astory that needs to be proven ‘essential’, but it deserves to be emphasized that which
the essentiality of story components is gradual and depends on the other available
evidence.
In sum, the second critical question for rational fact finding is as follows.
(2)

Is the story sufficiently supported by evidence?
There might be essential elements of the story which are not supported byarguments based on evidence.

Has the story about the murder of Nadia on October 1, 2002 been sufficiently
supported by evidence? In the verdicts, the following evidence information isprovided, where we specify which part of the story it supports:
–

–

–

–

The fact that Pascal has been in touch with his work is supported by telephonerecords (a call was made from the house to Pascal place of work) and by atestimony of Pascal’s colleague. The colleague has testified to the police and at
the court hearing that there is no doubt that he has talked to Pascal over thephone and that Pascal called in sick, although he did not sound ill.
That Nadia was making a phone call follows from the statement of the friend
who has heard her scream. The earphone of the phone was lying next to Nadia’s
body, the phone was on the kitchen counter.
The exact circumstances surrounding the murder itself, that is, the shooting of an
Uzi in the corridor and in the kitchen and the dragging of Nadia’s body, follow
from the bloodstains, bullet parts and shells found in the house. Also an Uzi’ssawn-off barrel, cartridges and cartridge clip were found in Pascal’s room.
That Pascal is the one who actually committed the murder, is supported by thefollowing:–––

An intercepted telephone conversation between Pascal and his father points
out that Pascal told his father that he killed Nadia after an argument about
the rental agreement.
A statement by Pascal’s father, who claimed that in January 2003 Pascal had
told him about a disagreement between Nadia and Pascal about the dryer andwashing machine and that he went crazy because he had been drinking.

The circumstances surrounding Pascal’s flight, that is, the facts that he drove
Nadia’s car off the road’s bank and then fled into the forest, is supported by thefollowing:–

Witnesses have stated that a man fitting Pascal’s description drove the carthat was steered off the ramp.

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Solving a Murder Case by Asking Critical Questions–––

Scent tests showed that Pascal sat on the driver’s seat and had touched thegear.
An intercepted telephone conversation between Pascal’s mother and brotherreferred to the fact that Pascal thought someone tried to cut him off at the
motorway’s access ramp.
A statement by an unnamed relative of Pascal referred to an alleged pursuitby a helicopter.

This list of evidence is taken directly from the verdicts.28
The main evidential gaps in the Nadia story are Pascal’s motives and the relation
between these motives and his action, shooting Nadia. For example, exactly why the(seemingly trivial) disagreement caused Pascal to shoot Nadia is at first left
unexplained and no evidence is mentioned for the fact that the shooting caused
Nadia’s death. Pascal’s motives for the murder are further dealt with when looking
at the plausibility of the story (critical question 4 in Sect. 4.4.). That the shooting
was the cause of death can probably be supported on the basis of autopsy report on
Nadia’s body, but this is not mentioned in the verdicts because it was no issue in thecase. In sum, critical question 2 has been satisfactorily answered.
4.3 Insufficient Support of the Relevance and Evidential Force of Piecesof Evidence
The next issue to consider is the strength of the evidence and its relevance forthe facts in the story. For this, we have to look at the evidential inferences from theevidence to the facts; in Fig. 2, for example, the inference steps are based on the
Witness Testimony argumentation scheme and two other generalizations. In orderto determine the relevance and probative force of a piece of evidence, thesegeneralizations and schemes warranting the inference steps should be made explicit.
Because warranting generalizations might express implicit biases or prejudices (e.g.
‘‘a confession is often true’’, cf. Wagenaar et al. 1993), it is important to determine
whether and, if so, on which grounds a scheme or generalization is considered to bevalid (i.e. provide the backing to the warrant, Toulmin 1958). As was discussed in
Sect. 3.1, schemes may be grounded in, for instance, logic, epistemology,29 scienceand law.
The general validity of a warranting scheme or generalization does not imply thatin the concrete situation the inference from evidence to conclusion can be made;there may be exceptional circumstances that exclude the use of the warranting
scheme. For well-known argumentation schemes, the critical questions point to such
typical exceptions (e.g. the witness lied or does not accurately remember, Sect. 3.1);
in the case of more specific generalizations, these exceptions will have to be
imagined on a more ad-hoc basis. For example, an exception to the generalization‘if person x was in a car at time t and someone looking like x has been seen in that28

Pennington and Hastie (1993) have shown that the chronological ordering is more convincing than anarbitrary ordering.

29

Freeman (2006) has provided a classification of types of warrants based on epistemic considerations.
He distinguishes a priori, empirical, institutional and evaluative warrants.

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car at time t, then it is likely that the person in the car at time t was x’ (Fig. 2) would
be if x has an identical twin y. In that case, it would be just as likely that y was in the
car at time t.
Summarizing, we find the following critical questions:(3)

Is the support that the evidence gives to the story sufficiently relevant andstrong?
(a)

Are the reasoning steps from evidence to the facts in the story justified by
explicit warranting schemes or generalizations that are valid andgrounded?
(b) Are there exceptions to the use of the schemes and generalizations that
undermine the connection between evidence and facts?
Often, common argumentation schemes (such as the scheme for Witness
Testimony or Expert Opinion) need not be explicitly stated. But the possibility of
exceptions can never be neglected. In our case study, most reasoning steps are basedon plausible schemes or generalizations. Perhaps the use of the scent test (Fig. 2) asa basis for drawing conclusions is the most controversial.30 If we consider thecriticisms concerning these scent tests well-founded, then we must conclude that thescent tests cannot be used to support the conclusion that Pascal was in Nadia’s car(critical question 3a).
With respect to most of the listed pieces of evidence, we need not assume that
there are exceptions to the underlying rules (critical question 3b) and we can infer
the events of the story supported by the evidence. One exception here is Pascal’s
father’s testimony: it might very well be possible that the father is biased when
testifying about his own son (critical question 3 for the Witness Testimony
Scheme). However, in this case there was other corroborating evidence (theintercepted telephone conversations) so it seems that Pascal’s father told the truth in
this case.
4.4 Insufficiently Critical Assessment of the Story
Now that we have considered questions 1, 2 and 3, we are in the following position:
there is a sufficiently clearly delineated account of the facts (the story), of which as
many as possible have evidence supporting them, of which the relevance andstrength has been established. The argument about the case as-a-whole can befurther improved by critically analysing the story and showing that there are no
viable alternatives.
One way of analysing a story is to look at its coherence. In Sect. 3.2, we saw thatstory schemes play an important role in determining this coherence: they allow us todetermine whether a story is complete (i.e. have all the essential parts of thecorresponding story scheme) and they have associated critical questions which point
to typical sources of doubt. Note that a story should fit a valid story scheme just as
an inference should be based on a valid argumentation scheme. For example, a story
30

The tests raised controversy in another well-publicised Dutch case, namely the Deventer Moordzaak.

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that follows a pattern where a conspiracy by the state against the accused issuggested, for example, is less coherent because such a pattern of actions is unusual.
Just as arguments are not always based on well-known argumentation schemes,
stories are not always be based on (valid) story schemes: in Sect. 3.2, we discussed
three ways of performing abductive reasoning, two of which (reasoning with similarcases and constructing completely new explanations) do not provide us with a story
based on a general scheme. In order to test a story’s coherence, we can therefore, notalways rely on critical questions associated with a scheme but we need also look at
the consistency of the story as well as the plausibility of the individual causal
relations and events in a story. For example, a story which reports that aliens landedon earth or a story which says that the victim’s death was caused by her being shotwith a ballpoint pen using a makeshift crossbow is less plausible and thus lacks
coherence.31
An assessment of the coherence of a story is to a large extent independent fromthe evidence available and can be based on our general expectations about the world(i.e. people do not usually shoot someone over a simple disagreement, shooting
someone from close range might kill them). However, there always is the danger ofpreferring a ‘‘good’’ story (i.e. a coherent one) to a ‘‘true’’ story (i.e. supported bystrong evidence) (Bennett and Feldman 1981). It is therefore, important toemphasize that the belief in a story must first and foremost depend on the extent towhich the evidence supports the story. The coherence of a story plays an importantrole when there are evidential gaps: an unsupported fact that is part of a coherent
story is more believable than one which is part of an incoherent story. Furthermore,in a case where the coherence of a story is lacking, this should be countered byparticularly solid evidence. Thus, a critical examination of the coherence of a story
might push the search for further evidence, as will be shown in the example below.
In addition to analysing the coherence of the story, we should also determine
whether there is evidence that refutes the story, that is, whether there are arguments
based on evidence that attack the story. There can be evidence against the facts inthe story itself, or evidence against facts that follow from the story (story
consequences). These story consequences are not part of the story itself, but causallyfollow from it. For instance, when according to the story the suspect fled from thescene of the crime while bleeding heavily, one story consequence is that there areprobably traces of blood at the crime scene. If no evidence for this is found, thebelievability of the story is reduced. Now, the fourth critical question can be phrased
as follows:(4)

Has the story itself been sufficiently critically assessed?
(a)Is the story sufficiently coherent? Are there elements missing? Are there
implausible events or causal relations? Is the story inconsistent?
(b) Is there evidence that refute elements of the story?
(c) Have story consequences been used to test the story?

31
This second example is based on an actual Dutch case, aptly named the ‘‘Ballpoint-case’’ (Feteris1999).

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Let us elaborate these questions for our example case about Nadia. We start withcomponent 4a: the coherence of the story. Something that at first sight is implausible
is the assumption in the story that the disagreement over the washing machine led
Pascal to murder Nadia. No reasonable person would assume that a disagreement
over washers and driers would lead a person to murder someone, so the causal
relation between the motive (disagreement) and the action (murder) is implausible.
In the previous section we argued that less plausible stories can be held true, as longas they are supported by strong and relevant evidence. In the case, the causal
relation is supported in part by the tapped phone conversation that suggests that
Pascal went berserk under the influence of alcohol. This makes the story morecredible, as it is well known that people who have been drinking can get overly
aggressive. Still, given the seriousness of what has happened, more is needed.
In its decision, the court of appeal inadvertently elaborates on Pascal’s tendency
to react rather violently in response to what most consider to be futile causes. In thedecision, a report of a psychiatric observation clinic is discussed; it is used toprovide support for the decision to keep Pascal under psychiatric surveillance. The
report of the PBC explains that Pascal has a disorder by which ordinary events makehim feel seriously threatened and react with disproportionate violence. From arational perspective, the report can be viewed as support for the fact that Pascal has
a tendency to react violently. Assuming that Pascal has this tendency, the events
surrounding the death of Nadia and its cause are suddenly a lot less incredible,
especially if we also take into account that Pascal had been drinking.
Another part of the story that on closer inspection might be regarded asincredible, is that Pascal has killed Nadia with an Uzi. Even if he had an Uzi
available, shooting one requires training, in particular in the purposive way as
mentioned in the story. On the other hand, one could say that someone who owns an
Uzi will probably know how to use it. The court of first instance mentions inconnection with another murder of which Pascal was a suspect that Pascal learnt
how to use an Uzi when he was in military service. This fact can be used to takeaway doubts about whether Pascal could shoot to kill, as in the case of the murder ofNadia.
Critical question 4b concerns counterevidence against the story. We already saw
in the example in Fig. 3 that Pascal denied he killed Nadia. More specifically, heclaimed he was in Poland at the time of the killing. Now, in this case Pascal’s claim
can be seen as a simple refutation of the main story: Pascal being in Poland andkilling Nadia at the same time cannot be part of the same consistent story. However,as was discussed in Sect. 2.2., this refuting claim can also be regarded as a (arguably
very simple) alternative story because arguments and stories are communicating
vessels. In Sect. 4.5., we will therefore, further analyse Pascal’s statements as analternative story.
Finally, the story consequences should be tested. The perpetrator, whoever it may
be, shot Nadia at close range and has subsequently dragged her body to anotherplace. So it is highly likely that the perpetrator would have blood on his hands,
clothes and shoes. It is hence quite possible that the offender’s shoeprints can befound in the house. If the offender then stepped into her car, there can also be tracesof Nadia’s blood in or on the car. The ruling of the court stated that indeed123

Solving a Murder Case by Asking Critical Questions

shoeprints were found in the house and that there was blood on the door lock and thefloor mat on the driver’s side of the car. The questions to be asked are then whether
the shoeprints are Pascal’s, and whether the blood on the car is Nadia. The evidenceshows that both can be answered positively. The shoeprints were probably made by
Reebok shoes and Pascal has stated that he indeed owned shoes of this brand, andthat he was wearing them when he left the country briefly after October 1. A
comparative DNA analysis showed that the profiles of the blood found in and on the
car matched Nadia’s profile.
4.5 Insufficient Attention for Alternative Accounts of the Facts (Tunnel Vision)
In the hybrid theory (or any theory of Inference to the Best Explanation for thatmatter), sufficient attention should be paid to possible alternative scenarios of what
has happened. So-called ‘‘tunnel vision’’ (i.e. focusing too much on one
interpretation of the facts) can and has lead to miscarriages of justice in the past.
A serious search for alternative scenarios is needed. These alternatives may beprovided by the opposing party at trial, but it is also important that the investigators
or decision makers themselves actively consider different accounts of what may
have happened. Story schemes might be of help in this respect, as they provide
guidelines or templates for possible stories. However, care should be taken that the‘‘stock’’ of story schemes is big enough: considering alternatives based on only asmall set of story schemes is also a form of tunnel vision, and as was argued in Sect.
3.2, one might have to imagine totally new hypotheses when no relevant schemes
are available. Note that alternatives should not only be actively sought, they should
also be adequately supported by evidence and analysed. Essentially, for any
alternative story we should ask critical questions 1 through 4. In the case of a verdictin a case, it should then be shown that the alternative stories are of a lesser quality
than the main story that fits the verdict. There are no hard-and-fast rules that
determine when one story is better than another. That is, we cannot safely say that,for example, a story that is supported by two pieces of evidence is better than a story
supported by one piece of evidence. If, for instance, the first story is a highly
incoherent account supported by statements of two witnesses who are suspects
themselves and the second story is highly coherent and supported by hard evidence
such as CCTV images, we would argue the second story is the better one.
Evidential gaps often also lead to situations where the choice between
alternatives is complicated. For example, when the prosecution claims criminal
intent but the defence argues this is not the case, the judge or jury is faced with two‘‘alternative’’ stories which are essentially the same save for the single element ofmens rea. Without any additional evidence pointing to the suspect’s intent, thechoice between these alternatives is hard to make. In the Netherlands, the situation
where there are two alternatives which are both compatible with the same evidence
is called a ‘‘Meer-en-Vaart’’ situation (after the Meer-en-Vaart case, Dutch Supreme
Court February 1, 1972, NJ 1974, 450). The Dutch Supreme Court has decided thatin such Meer-en-Vaart situations the question why the one story should be chosenover the other has to be explicitly addressed.

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To summarize, quantifying the quality of stories is a hard, if not impossible, task
and the comparison of stories is a complicated pursuit. Because of this, it isimportant that all stories and their supporting arguments are dialectically analysedusing critical questions. Furthermore, any reasons for choosing one story over theother should be made explicit. Thus, we have the following critical question:(5)

Have alternative stories been sufficiently taken into account?
(a)

Has a sufficient search for alternative explanations been performed, notonly in the investigative phase, but also in court?
(b) Have the alternatives been sufficiently analysed? Are there explicit
reasons to choose one story over the alternatives?
In the Nadia case, Pascal told the alternative story that he was suffering fromamnesia and could not remember what happened on October 1. He claimed to havebeen kidnapped and taken to Poland, although by unknown persons and for
unknown reasons. First, this can hardly be considered a story (cf. our criticalquestion 1 that requires a sufficiently specific account of the facts); in the previous
section, we therefore, already presented part of this story (that Pascal was in Poland)
as a simple refuting argument. However, let us for the moment assume Pascal’s‘‘account’’ is an alternative story. It is immediately apparent that Pascal’s story is
not nearly as coherent and well-supported as that of the prosecution. As for thestory’s coherence (critical question 4a), several crucial elements are missing, suchas the identity and motive of the kidnappers. Furthermore, the story is incoherent:
Pascal claims to have blanket amnesia but he does remember he did not kill Nadia
and was in Poland. As for evidential support (critical question 3), only Pascal’s
statement supports his story and there was no corroborating evidence for, forexample, the kidnapping having taken place. Also, the court explicitly refutes theamnesia defence (critical question 4b): it states it does not believe Pascal, because
Pascal has never sought medical help for his alleged amnesia. Thus, the court
explicitly refutes Pascal’s alternative.
4.6 Missing Weighing of Reasons
Finally, a general caveat is in place: any conflicting reasons must be weighed. Theremay, for example, be conflicting arguments based on evidence (e.g. two witnesses
who make opposite statements about the suspect’s whereabouts). Conflicting
reasons do not only exist at the level of arguments for or against individual events,
but also at the level of stories. For example, there might be reasons for and against a
story as a whole or reasons for choosing one story over another. When there are
explicit grounds that can decide the weighing of such opposing reasons, they should
be given. The stronger and more relevant the reasons are, the more important it is todecide explicitly how they are weighed against each other.32 The final criticalquestion can now be phrased as follows:32
The exact role and nature of the weighing of reasons goes beyond the goals of this paper. In ourperspective on the weighing of reasons, the issue whether certain given pros outweigh given cons is itself
open for argumentation. For instance, in the law, precedents can sometimes be used to argue how certain123

Solving a Murder Case by Asking Critical Questions(6)

Have all opposing reasons been weighed?
Have all considerations that are used to weigh opposing reasons been madeexplicit? Has this been done both at the level of individual facts and events andat the level of stories as-a-whole?

In the Nadia case, there was no difficulty in the balancing of reasons at the levelof stories. Pascal’s ‘‘story’’ was so implausible and badly supported that it could beconsidered as refuted by itself (because of its incoherence), even without
considering the plausible and well-supported story of the prosecution. As an
example of a weighing of individual events, we mention the smell test that played arole in determining the circumstances of Pascal’s flight. By itself, such a smell test
may not be considered sufficiently satisfactory, but in conjunction with otherevidence (testimony, intercepted telephone conversation, traces of blood) itnevertheless helped to support this part of the story of the prosecution.

5 Conclusion
In this paper, we have proposed a series of critical questions for the hybrid
argumentative—narrative theory of reasoning about the facts and the evidence inlegal cases. Some of these critical questions point to the argumentative part of a
hybrid case (in particular critical question 2 about the sufficient support of theevents, and question 3 concerning the relevance and strength of the support). In thismore argumentative part of an analysis, our critical questions for the case-as-awhole are supplemented by the critical questions associated with argumentation
schemes as studied in argumentation theory. There are also general criticalquestions that are strongly connected to a narrative style of analysis (in particularquestion 4 about the coherence of the supported story, and question 5 about theconsideration of alternative stories). Analogous to the argumentative side of thetheory, these critical questions are supplemented by critical questions for individual
story schemes. Thus, we expand on the analytical tools for analysing legal
argumentation that are currently available, such as Walton’s argumentation schemes(Walton 2002), Wigmore’s charts (Wigmore 1931; Anderson et al. 2005) and theAmsterdam school’s pragma-dialectical analysis (e.g. Feteris 1999).
Our hybrid theory and the associated critical questions show that the dialecticalargumentation that is involved in reasoning on the basis of evidence is an intricate
process that cannot be modelled appropriately using just syllogistic arguments of theform A therefore B. We have shown how two kinds of general knowledge about theworld play a role: (1) defeasible argumentation schemes that specify which kinds ofreasons support which kinds of conclusions (such as the witness testimony scheme),and (2) story schemes that specify which clusters of facts and events are plausible
Footnote 32 continued
reasons must be weighed. See also Wellman (1971), Naess (1978), Govier (1999), Feteris (2008), Hage
(1996, 1997), Verheij (1996). The debate on the weighing of reasons has recently been revived by the
Symposium on Conductive Arguments, organized at University of Windsor in 2010 (about which a
special issue of the journal Informal Logic is in preparation).

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and coherent combinations that can be expected to happen (such as the restaurant
script or the murder story scheme). Here our approach echoes Twining when he said
that the knowledge humans use when arguing cannot just be captured asconditionals; rather it is a ‘a complex soup of more or less well grounded
information, sophisticated models, anecdotal memories, impressions, stories, myths,
proverbs, wishes, stereotypes, speculations and prejudices’ (Twining 1999, p. 91).
One of the lessons learned from the work on the hybrid theory is that stories andarguments are to some extent ‘‘communicating vessels’’: when dealing with thecomplex reasoning involved in large criminal cases, a narrative approach works bestfor some points of a case, while in other instances an argumentative approach ismost natural. However, for a deeper understanding of the connection between
argumentation and narrative, it seems to be required to develop a further integrationof both, in order to make their differences and similarities more clear-cut.
Meanwhile, our hybrid approach allows for the flexibility of the separate
argumentative and narrative approaches whilst at the same it uses arguments andstories as complementary tools for complex reasoning. The case studies in this text
and by Bex (2011) accentuate the value of a hybrid, argumentative-narrative
analysis of reasoning about the facts in criminal cases.
We believe that stories and story schemes will play an important role, not just forreasoning with evidence but in the field of argumentation in general. In particular,
we consider the following issues to be urgent topics of research:
1.

2.

3.
4.

5.

Elaboration of the notion of a story scheme. What are the properties of story
schemes that make them useful in argumentation? What is the role ofabstraction of stories and story hierarchies? When can a story be generalized toa story scheme? When is a story an instance of a story scheme?
Integration of argumentation and stories. Can argumentation and stories beconnected in a more fundamental way than in the hybrid theory? Can the idea of‘communicating vessels’ be fleshed out in a genuine integrated approach? What
are the limitations of integrating arguments and stories given their distinct roles?
Are there criteria to determine which elements of a story must be directly supported
by evidence, and which can be assumed in conjunction with the other facts?
Embedding in software support systems. Can sets of argumentation and story
schemes form the backbone of useful software support systems?
Repositories of argumentation and story schemes. Which (types of) argumentation and story schemes are relevant for argumentation? How do we extractsuch schemes from actual arguments and stories?
Case studies. Are real cases usefully analyzable using the hybrid theory? Arethey an appropriate source of argumentation and story schemes?

Some ideas about these questions have already been proposed by the current
authors and their collaborators. Questions 1 and 2 have been explored by Bex (2009,2011), Bex and Verheij (2010) and Verheij and Bex (2009). Van den Braak (2010)
has already shown that a tool which allows for ‘‘story-mapping’’ (cf. argumentmapping with schemes, Reed et al. 2007) can be of use in police investigations andpolice training (Question 3). Bex et al. (2003) and Walton (2002) mention a numberof argumentation schemes which can be used specifically in reasoning with123

Solving a Murder Case by Asking Critical Questions

evidence (Question 4). Bex et al. (2003) analyse a part of the famous Sacco and
Vanzetti case using argumentation schemes and Bex (2011) devotes a large part ofhis book to analysing a Dutch murder case using the hybrid theory (Question 5).
As can be seen, the focus in recent research has mainly been on arguments andargumentation schemes. We think these first ideas are a fertile ground on which new
research can be built, further exploring the use of stories in philosophical andcomputational theories of complex reasoning.

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