Before delving into the applications and relevant theories in Forensic Psychology in this case, it is first necessary to summarise the particulars of this case. This will allow for the evidence to be objectively assessed, and then broken down as the empirical evidence provided by the field of Forensic Psychology pertains to specific points. This will allow for the value of various aspects of the evidence on both sides to be assessed, which may result in a re-evaluation of the overall verdict. The psychological evidence will then be evaluated within the relevant theoretical framework, and these theories will in turn be critically analysed so that the degree to which the relevant findings and theories of forensic psychology can be used to interpret the meaning and weight of evidence in this case can be evaluated.
The defendant was convicted of murdering his wife, but appealed against conviction on the grounds that he was suffering from a mental illness and therefore was impaired substantially enough to meet the criteria for manslaughter, not murder. The appeal was dismissed. Although the defendant admitted killing his wife he did not give evidence at the trial, stating that he was not in a fit mental state. A voir dire by a medical expert, B, attested to the fact that the defendant ought not to give evidence due to his mental state, and when recounting this to the jury the judge ruled that no adverse inference should be drawn from this. The judge did however not allow evidence from B to be given at the trial. The evidence in support of the defence was given by three expert medical witnesses all attesting to the deteriorating mental state of the defence and that the criteria for diminished responsibility were satisfied. No medical testimony disputed this. Evidence admitted by the judge against the defence came from the defendant’s daughter, S, who recounted a conversation in which the defendant admitted assaulting the victim on a prior occasion. This was taken as evidence of the defendant’s bad character. During the trial there was some discussion of the definition of the term ‘substantially impaired’; the defence counsel defined the term as anything ‘more than trivial[ly impaired]’ but the judge refused this definition and declined to give the jury any further guidance as to the legal definition of this term.
A verdict of manslaughter would suggest that the defendant was not able to fully understand the nature of what he was doing, make a rational decision and exercise self-control (Morse, 2003). Of course the legal definition of ‘substantially impaired’ is also relevant; as it is defined by the English Homicide Act (1957) substantial impairment is constituted either by a ‘common sense’ standard or by any degree of impairment which is more than trivial but less than total (Prevezer, 1957). Whether the defendant reaches the threshold for these definitions of substantially impaired will decide whether he is convicted of manslaughter or murder.
One issue raised by the defendant in the appeal was that although the judge did explicitly state that the jury was not to draw any condemning inference from the defendant’s lack of testimony, he failed to remind the jury that S’s evidence should be considered with caution, because the defendant was not able to give any account of the alleged conversation. According to the literature in forensic psychology there could be valid grounds to this claim, however the claim itself could also be redundant entirely. This is because jurors do indeed evidently find it difficult to evaluate the weight of evidence and draw inferences appropriately (Thomas and Hogue, 1976). Thomas and Hogue (1976) developed a decision-making model for jurors, showing broadly that the weight jurors will ascribe to evidence varies across the population according to a variety of factors relevant to the characteristics of the jury. In this model the decision threshold which defines whether the jury votes for the plaintiff or defendant varies little across the population but may vary between cases and be affected by factors such as instructions to jurors. This latter point is very important because it addresses the effect that instructions to the jury can have, even a small effect could have made a substantial difference to the way the jury regarded evidence. Evidence suggests that this is particularly the case with emotionally-charged evidence which is pertinent to this case, Cush and Delahunty (2006) found that mock jurors who received no pre-evidence instructions to consider emotionally evocative evidence (gruesome photographs) dispassionately or with caution gave more verdicts in favour of the victim and scored higher on measures of victim compassion and crime negativity than did jurors who did receive such instruction.
Embedded within cognitive theory this evidence supports the defendant’s position on this point; without all of the pertinent evidence with the appropriate weights the juror as a sense-making machine would not be able to reach an informed decision (Pennington and Hastie, 1991). The heuristics and biases approach (Griffin, Gonzalez and Varey, 2001) views decision-making, thought and perception as vulnerable to various cognitive biases and distortions from mental archetypes. One such source of bias has been dubbed ‘WYSIATI’, or ‘what you see is all there is’. This notion is important in a forensic context because the jury will naturally find it difficult to take into account evidence that is not readily presented to them (Neal and Grisso, 2014) especially when presented with material evidence which contradicts it.
Another point to consider is the value of S’s evidence; factors which may be important to consider are the age of the witness (Ceci, Ross and Toglia, 1987), the power of hindsight and the nature of reconstructive memory (Leippe, 1980). According to a retrieval theory of memory, recognition and recall styles of memory are possible through a resonance-style spreading-activation pattern of retrieval attempts (Ratcliff, 1978). When a search of memory in this way is performed, certain archetypes or contextual information and assumptions about the objects in memory may fill in gaps or add meaning; depending on the age of the witness this may be even more important, because young children are more susceptible to such biases (Ceci, Ross and Toglia, 1987; Leippe, 1980). There may have been subtleties in the alleged conversation with the defendant which would reinterpret the meaning, especially in light of the defendant’s alleged mental illness which S could have missed in her memory of the conversation.
Even if the judge had instructed the jury to treat S’s evidence with caution though, the question is what effect would this have had on the verdict. The answer would seem to be that even though it may have changed the jury’s perception of the evidence (Cush and Delahunty, 2006), this would not have substantially affected the verdict because the evidence of S was of limited significance in the first place because of the strength of other evidence that the defendant had abused the victim. A cognitive decision-makin framework would see people evaluating this evidence overall in favour of the victim (Pennington and Hastie, 1991). In addition to this it was made clear to the jury that the case of the defendant was that he had not abused the victim. This makes it a somewhat trivial point in the overall case.
Cognitive theory is useful in the context of forensic psychology because it provides a framework for the decision-making process to be understood, and an opportunity for the value of evidence to be quantified. The theory does view human beings as rational agents who are able to objectively consider evidence, simply adding additional weight to emotional evidence. This could be seen as reductionist as it ignores a wealth of human experience and much of the cultural meaning inherent in cases such as this one. The spreading-activation theory of memory also has its opponents. Some memory researchers prefer to view memory errors as arising from consolidation or encoding errors (Squire and Alvarez, 1995). Both are useful in a forensic psychology context but it is important to remember that the evidence is interpreted theoretically, and there must still be a weight assigned to evidence based on theory. It must therefore be acknowledged that the interpretation of evidence is at least somewhat arbitrary based on these theories.
A second point in the appeal was that the judge was supposedly wrong to not allow the evidence of B to go before the jury. The value of expert witnesses is debateable in the literature, assuming that their professional opinions within their fields are valid and reliable, the problem arises with the effect their testimony has on the jury. Expert testimony usually affects the credence that the jury gives to the testimony or stance of the individuals being evaluated, and in this case the evidence of B may well have contributed to the judge’s decision to instruct the jury to draw no condemning inference from the defendant’s lack of testimony. Due to certain cognitive biases, the message an expert tries to convey may not be received by the jury as intended, which may vindicate the judge’s decision to not allow B’s testimony. Jury members will often ascribe disproportionate impact to expert testimony (Krafka, Dunn, Johnson, Cecil et al., 2002), meaning the intended message is exaggerated or otherwise distorted resulting in jurors who may believe something contrary to what the literature on mental illness suggests. B had stated that the defendant was not in a fit state to give testimony, and attested to the reality of his mental illness and deteriorating mental state despite the usage of antipsychotic medication. This last point may be of particular importance because members of the general public may not have a full understanding of the research into the effects of antipsychotics (Jorm, Korten, Rodgers, Pollitt et al., 1997) which B presumably did have. If the jury believed that antipsychotics could cure the defendant’s mental illness then this could lead to them drawing a condemning inference.
The weight that B’s evidence would have had is in question though because of the already substantial amount of evidence in support of the existence and chronic worsening of the defendant’s mental illness. This is an issue because if the jury was already convinced that the defendant was indeed mentally ill at the time of the killing and still voted to convict the defendant of murder then the impact B’s evidence may have had is a moot point. The only remaining question is whether B’s testimony would have added anything to the testimony of the other experts due to the voir dire examination. It does seem unlikely that the testimony of B would have differed significantly from the other experts, and due to the evidence suggesting that the individual persuasive ability of experts has more of an impact on jurors than the content of their message (Bank and Poythress, 1982) the judge was probably right to not allow the additional expert testimony.
A criticism of most of this research is that it mostly uses mock jurors, and also the mock cases obviously involved different experts and circumstances to the one in question. This means that the effect may be more or less pronounced in this scenario, but the evidence is from a very relevant context and is extremely likely to still be useful. The only potential problem lies in the participants not taking the mock case as seriously as they would a real case.
The general population may not have a good understanding of mental illness or mental capacity as these terms are defined in legal discourse (Jorm, 2000) which did necessitate at least some expert testimony. Another point is that the judge did not give any contrasting definition for the term ‘substantially impaired’ when the defence counsel offered the definition of ‘anything impairment more than trivial’. Although this was submitted as grounds for appeal, the evidence suggests that if anything this point would have resulted in the jurors adopting a standard of impairment that was too liberal by legal standards. This is because jurors and indeed people in general are not as able to disregard presented information as readily as most people believe (Lieberman and Arndt, 2000). According to theories in social psychology, hindsight bias and belief perseverance can lead to jurors actually relying on inadmissible evidence more than other evidence (Lieberman and Arndt, 2000). This is very useful research in this context because it highlights the importance of presented information; the definition offered by the defence counsel will be given inappropriate attention. Since the verdict was still to convict, this suggests strongly that the court was right to dismiss the appeal.
In light of the strength of the evidence and theory reviewed and the applications in this case, it is clear that the second and third points submitted by the defendant in the appeal were properly rebuffed by the judge, in fact the evidence suggests that these issues would have worked in the defendant’s favour if the judge had responded differently. As for the first point, it appears from the research that any effect on jury perception would be negligible, although there is some conflict in the literature as to the effect of instructions of limitation from the judge.
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