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Author: Paul Troop

Jury Decision-Making: What’s the Story?

Updated Thursday, 18 May 2023

What is the 'story model' theory - and how can it be applied to understanding jury decision making?

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Why would we need a theory to understand jury decision making? To answer this, it helps to think about why we might be interested in understanding juries in the first place. One plausible reason is that we might want to reassure ourselves that they are making reliable decisions. Or, to put it differently, to see where any shortcomings in jury decision-making lie, and, if possible, to overcome these shortcomings. We know from both everyday decision making and specialist research into decision-making in the legal context that people make mistakes and they are sometimes subject to influences that we find objectionable. One way to identify such shortcomings is to do empirical research where we manipulate the counterfactuals (eg, by having one scenario with the item of interest and one without) and to repeat the research a number of times (because with small samples there can be random influences or 'noise' and larger samples help to drown this out).


But empiricism without theory is indescribably onerous. There are two main reasons for this. The first reason is that there are an infinite number of tests that we could carry out, and many of them will be a waste of time. Eg, should we test what colour shirt a juror wears? This is a particular problem in the jury context when jury research is so complicated and costly. We want to spend our limited resources wisely. So researchers reflect carefully on what they already know and try and articulate theories that would be most likely to find unexpected behaviour by juries. A second, somewhat related, reason is that we want to be able to use our research to make generalisations to other scenarios that we have not yet tested. A theory allows us to make inferences that 'go beyond the information given'. A policy maker would not be very impressed if each time they asked a researcher to answer a 'what if' question that researcher had to go out and conduct another round of experiments. A theory might not be bulletproof, but a mostly reliable theory is still useful.


In the psychological domain, the most popular theory of jury decision making is the so-called 'story model' (Simon, 1998; Devine, et al., 2001; Zamir, et al., 2014; Levett, & Devine, 2017). I'm now going to explain this theory and highlight a few queries about it.


The Story Model


The story model is most closely associated with Nancy Pennington and Reid Hastie, though a number of other theorists have also suggested similar theories (Hastie, et al., 1983; Pennington, & Hastie, 1992; Anderson, et al., 2005).  In the first stage, a juror examines the evidence presented at the trial and makes inferences about what they think happened. Obviously the evidence is incomplete, so a range of explanations are compatible with it. Jurors therefore need to use their sense and experience to make sense of it. What they make of it depends a bit on their background (Hastie, et al., 1983). For example, a juror who has had bad experiences with the police might be less inclined to believe police evidence compared to somebody whose experiences have all been positive. Interestingly, story model theorists generally put variation in decision-making down to the background experiences of jurors (a point we will return to below).


The story model is so called because the theory specifies that jurors conclude the first stage by settling on their preferred story, basically a model of what happened in a narrative form. For example, a story might be: 'X murdered Y because he was in financial difficulties and stood to inherit from Y.' Another might be 'X was framed for Y's killing by Z as Z was next in line to inherit if X was found guilty' (X, as a murderer, would be prohibited from inheriting because of the Forfeiture Act 1982). The juror's preferred story could be one of the models suggested by the prosecution or defence, or one they thought of themselves. In comparing stories, or coming up with their own, jurors are assumed to use 'certainty principles'. One such certainty principle is that of 'coverage' (Pennington, & Hastie, 1991). Pennington and Hastie assume that a story that has greater coverage (i.e. that explains more of the evidence) is more likely to be accepted, all things considered.


The second stage of the story model is that of learning the relevant verdicts (Hastie, et al., 1983; Pennington, & Hastie, 1991). The judge, as the tribunal of law, specifies what verdicts are linked to what facts. This might be simple, such as where there is a single offence which the prosecution need to prove all elements of beyond reasonable doubt, or it could be more complicated where there are several offences, defences, alternative counts, evidential and legal burdens, etc.


The third and final stage is where the jury engages in a process of categorisation, applying the legal categories to the preferred story, to settle on a verdict (Pennington, & Hastie, 1992). This process is a bit like a deductive syllogism (i.e.: ‘All men are mortal. Socrates is a man. Therefore Socrates is mortal’).


Loose Ends


Though many find the story model very appealing, there are a number of loose ends. We will examine a few here.


One loose end is the group dynamic. As anybody who has enjoyed the film '12 Angry Men' will know, juries are more than the sum of their parts. That is, the final decision is not simply a product of the views of the 12 (or more) individual jurors. In England and Wales, there is a requirement for unanimity, so jurors debate the facts and try to seek consensus. As in 12 Angry Men, a jury can flip from 11-1 in favour of conviction to 12-0 in favour of acquittal. Story model theories admit that the theory is a little bit thin on this group aspect of jury decision-making, which is somewhat problematic given that the group dynamic is such a characteristic aspect of this type of process (Hastie, et al., 1983; Devine, et al., 2001; Diamond, & Rose, 2018).


Returning to the issue flagged up in the previous section, there is also a query about the influence of individual values. The story model seems quite formalist in its outlook. Formalism is quite a traditional and conservative approach to legal adjudication that assumes that the process is quite logical with few, if any, extraneous influences. Formalism was challenged in particular by the American legal realists who suspected that collateral influences such as the outlook of the judge (or juror) also influenced outcomes. The realists mocked formalism as 'mechanical jurisprudence' (Cohen, 1935) and there is quite a considerable body of empirical evidence that suggests that there are a wide range of 'extra-legal' factors that frequently influence adjudication. As such, any model of adjudication should account for these patterns, and here the story model seems to struggle.


Finally, there is a query about the role of stories themselves. Note that stories are not just factual models, but they are factual models with a very characteristic narrative form. That is, they feature stereotypical structures including characters with desires and intentions and so would be familiar to any person in the street (in a way that other models such as machine code or connectionist models would not). Story model theorists sometimes seem to indicate that the story form is either integral to the individual juror's cognitive process, or at least that there is a particular value of the story form to the juror's personal cognition (Pennington, & Hastie, 1991). However, it's not clear what this value really is. The same model can be represented identically in different forms, say stories, digital computer code, connectionist systems, or neuronal flesh-and-blood. Here again there seems to be a chapter missing from the story.


So, while the story model might be the most popular theory of jury decision-making, and it might also be the most complete theory that we have, there is still a lot more to be told.


References


Anderson, T., Schum, D. and Twining, W. (2005) Analysis of Evidence. 2nd edn. Cambridge: Cambridge University Press. Available at: http://ebooks.cambridge.org/ref/id/CBO9780511610585.

Cohen, F.S. (1935) ‘Transcendental Nonsense and the Functional Approach’, Columbia Law Review, 35(6), pp. 809–849. Available at: https://doi.org/10.2307/1116300.

Devine, D.J. et al. (2001) ‘Jury Decision Making: 45 Years of Empirical Research on Deliberating Groups’, Psychology, Public Policy, & Law, 7(3), pp. 622–727.

Diamond, S.S. and Rose, M.R. (2018) ‘The Contemporary American Jury’, Annual Review of Law and Social Science, 14(1), pp. 239–258. Available at: https://doi.org/10.1146/annurev-lawsocsci-110316-113618.

Hastie, R., Penrod, S. and Pennington, N. (1983) Inside the Jury. Cambridge, Mass: Harvard University Press.

Levett, L.M. and Devine, D. (2017) ‘Integrating Individual and Group Models of Juror Decision Making’, in The Psychology of Juries. Washington, DC, US: American Psychological Association, pp. 11–36. Available at: https://doi.org/10.1037/0000026-002.

Pennington, N. and Hastie, R. (1991) ‘Cognitive Theory of Juror Decision Making: The Story Model, A’, Cardozo Law Review, 13, p. 519.

Pennington, N. and Hastie, R. (1992) ‘Explaining the Evidence: Tests of the Story Model for Juror Decision Making’, Journal of Personality and Social Psychology, 62(2), pp. 189–206. Available at: https://doi.org/10.1037/0022-3514.62.2.189.

Zamir, E. et al. (2014) ‘Judicial Decision-Making’, in E. Zamir and D. Teichman (eds) The Oxford Handbook of Behavioral Economics and the Law. Oxford University Press. Available at: http://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199945474.001.0001/oxfordhb-9780199945474-e-026 (Accessed: 12 November 2015).

 

Forfeiture Act 1982 c.34



 

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