Verdict spotting: investigating the effects of juror bias, evidence anchors and verdict system in jurors.

The Scottish verdict of not proven represents a second acquittal verdict which is not legally defined. Existing research into the influence of the not proven verdict on jury decision making is modest. The main aim of the current study was therefore to investigate the influence of verdict systems (two vs three) on juror decision making. The effect of pre-trial bias and evidence anchors on juror judgements were also examined. One-hundred and twenty-eight mock jurors listened to two homicide vignettes and were asked to rate their belief of guilt of the accused and to give a verdict in both trials. The results suggest that pre-trial bias was a significant predictor of both verdict choice and belief of guilt, whereas evidence anchors were not a significant predictor of either. Finally, both guilty and not guilty verdicts were given with increased frequency in the two-verdict system when compared to the three-verdict system.

Threshold point utilisation in juror decision-making.

This study aims to identify whether a model of juror decision-making (i.e. the threshold point model) that encompasses both rational and intuitive decision-making exists. A total of 60 participants were selected who are eligible for jury duty in Scotland. These individuals read nine vignettes and rated the evidence of each vignette separately by placing the evidence in either a guilty, a not guilty or a not proven (a verdict type specific to Scotland) counter. Participants were asked after being presented with each piece of information to state how likely they thought the suspect was of being guilty, on a scale from 1 to 100. The data are best described using a flexible model (i.e. a diffusion model) that allows for information integration. Future research should examine whether or not the diffusion model can explain cognitive fallacies, such as confirmation bias, that are commonly studied in decision science.

The bastard verdict and its influence on jurors.

The Scottish legal system is a unique jurisdiction, as jurors are able to give not proven verdicts in addition to the well-known Anglo-American verdicts (guilty and not guilty). The not proven verdict has never been legally defined, meaning that currently legal practitioners can only estimate why a not proven verdict has been given. The main aim of this study was to investigate if jurors violate the regularity principle, which is commonly incorporated in many rational choice models, by testing if the introduction of the not proven verdict has an impact on the outcomes given by jurors. In addition, this study aimed to test if the introduction of the not proven verdict has an impact upon how the not guilty verdict is perceived by jurors. In this study, 128 participants listened to two vignettes centred on homicide trials. Jurors could give one of two verdicts in one of the vignettes and one of three verdicts in the other vignette. The vignettes were counterbalanced in regard to how many verdicts could be given at the end of them. It was found that jurors in a three-verdict system were less likely to give a not guilty verdict in comparison to jurors in a two-verdict system, showing that jurors violate the regularity principle and that the not proven verdict may change how the not guilty verdict is perceived. The findings of this research have implications in relation to juror communication, article 6 of the European Convention of Human Rights and juror rationality.

Faith in thy threshold.

The current study focussed on the decision-making processes of jurors. The study investigated how jurors make a decision, if they integrate information within their decision-making process and if cue utilisation thresholds promote confirmation bias. To do this, 108 participants listened to one of nine cases. These participants were asked to give a likelihood of guilt rating after each piece of evidence, to state what the last piece of information was that they needed to make a decision and to give a final verdict at the end of a trial. The results highlighted that threshold decision making was being utilised, that information integration may allow thresholds to be reached and that thresholds may promote confirmation bias to reduce cognitive dissonance. In conclusion, this suggests that jurors integrate information until they reach a leading verdict, then the evaluation of information is distorted to support the leading threshold. Implications relate to legal instructions for jurors.

Are consistent juror decisions related to fast and frugal decision making? Investigating the relationship between juror consistency, decision speed and cue utilisation.

The aim of this study was to establish whether more consistent/accurate juror decision making is related to faster decision-making processes which use fewer cues - that is, fast and frugal heuristic processes. A correlational design was implemented with the co-variables: consistency of verdict decisions (participant decisions compared to the actual court verdicts), decision speed, and cue utilisation (the number of cues used to make a final verdict decision). Sixty participants read information about six murder trials which were based on real cases and whose outcome verdicts were deemed to be correct by the Scottish legal institution. Three of the cases had been handed down 'not guilty' verdicts, and three had been handed down 'guilty' verdicts. Participants read opening statements and were then presented with a block of prosecution evidence, followed by a block of defence evidence. They were then asked to make a final verdict. All three co-variables were significantly related. Cue utilisation and speed were positively correlated, as would be expected. Consistency was negatively and significantly related to both speed and cue utilisation. Partial correlations highlighted that cue utilisation was the only variable to have a significant relationship with consistency, and that the relationship between speed and consistency was a by-product of how frugal the juror was. Findings support the concept of frugal decisional processes being optimal within a juror context. The more frugal a decision is, the more likely jurors are to be to be accurate/consistent.