I believe that the strong reason for excluding character evidence is that juries may apply undue weight to this form of evidence. This may cause the jury to misinterpret if they have achieved a necessary threshold for attaining ‘proof without reasonable doubt.’
In this post, I present two arguments that support the thesis that undue weighting can make jury decisions unreliable. Despite this, I believe that strong grounds exist for this type of evidence to be included in legal trials. I present two rebuttals to the two arguments against inclusion of this form of evidence. These rebuttals form my argument that the problems raised can be overcome.
Introduction
The inclusion of certain kinds of evidence in a legal trial must be sufficiently deliberated-over. In the case of character evidence, on one hand character evidence has logically probative value,[1] however, it may be that the potentially prejudicial effect of this type of evidence outweighs that probative value.
From a Bayesian perspective, it makes sense to take prior probability in the general into account when determining the likelihood of an event being true or false in the particular. The Bayesian method of statistical inference may be able to inspire some confidence in our self-perception of our probabilities of doubt and certainty. For Bayesian estimation we rely on a priori probability, and then adapt it when some new evidences are presented. This gives us a wider frame of reference when determining likely probabilities. In a legal trial, incidences of prosecutors’ fallacy are hoped to be avoided. The aim is to keep the number of false-positives low so that innocent people do not get unjustly condemned. Surely then, if character evidence can help achieve greater confidence in our judgements it should be used in legal trials to inform juries whether or not they can confidently satisfied the condition of ‘proof without reasonable doubt’. Probative
However, it has been shown by Kahneman et al that it is not uncommon for individuals to commit basic mistakes when reasoning about probability.[2] For example, they show that people place undue weight on information that is easily retrievable or highly available. An example of this could be, for instance, a drop in the number of airline passengers after a highly publicized plane crash. The fact that the 24-hour news cycle has a propensity to keep emphasising the crash can make people imagine that it is very unsafe to travel by air, even though it has been proven that fatal accidents occur one hundred times more frequently when travelling by road.[3] As the memory of the crash slips out of consciousness, the number of flights sold increases, even though the probability of dying in a plane crash essentially remains constant throughout. The plausibility of this made-up example lies in its similarity to patterns we observe in real life situations. We often observe individuals, including ourselves, incorrectly applying too much probability on the chance of certain events heppening. Equally, this problem affects juries too.
In the next section, I will show that increased jury fallibility, by applying undue weight to character evidence, provides the strongest grounds for exclusion of character evidence. The placing of undue weight on this form of evidence can stem from a juror’s: a. uncertainty as to what a reasonable burden of proof threshold should be, and b. exposure to limited reference class of the defendant.
Grounds for Exclusion of Character Evidence
a. Character evidence alone could satisfy the burden-of-proof threshold for some Jurors.
It can be argued that introducing character evidence into legal trials can push a juror’s conception of guilt over a unreasonably low threshold of ‘proof beyond reasonable doubt’. This argument draws from the ambiguity of what constitutes ‘beyond reasonable doubt’ for a jury member.
Reasonable doubt refers to the doubt that prevents one from being firmly convinced of a defendant's guilt or the belief of the real possibility that the defendant is not guilty. Proof beyond a reasonable doubt, therefore, is proof of such a convincing character that you would be willing to rely and act upon it without hesitation in the most important of your own affairs.[4] It is the level of proof demanded by the legal system to allow a juror to support the conviction of an accused person in a criminal case.[5] However, it does not require absolute certainty.
There have been some strides towards quantifying the ‘proof beyond reasonable doubt’ standard of criminal law as a percentage probability. For example, one prosecutor (in People v. Ibarra 2001) attempted to explain it using a bar chart showing different sublevels of doubt: 60%: beyond a reasonable doubt; 70%: beyond a shadow of doubt; 80%: beyond all doubt; 90%: absolute certainty. Besides the arbitrary nature of the milestones, needless to say 60% is a very low bar for beyond reasonable doubt, as 40% chance of being wrong is a very significant minority.
I believe that it is conceivable that a jury member with this particular low threshold of ‘proof’ (60% certainty) could decide on a verdict of guiltymerely from hearing character evidence! This is especially worrying when it is known that some individuals have even lower conceptions of what constitutes proof ‘beyond reasonable doubt’. For instance, a survey of over one hundred adults was conducted to gauge their attitudes towards presumptions of guilt and innocence and what probability constituted ‘beyond reasonable doubt’. All but two respondents replied that they required between 50% and 99.9% (some lying below the 60% threshold) with most respondents replied with higher probability preferences ranging from 80% to 99%. One interesting outlier was an individual who only required 30% to make a conviction!
This is interesting when we take pre-trial presumption of guilt into consideration. Weinstein notes that the innocent until proven guilty principle is theoretically sound but in practice it can only be weakly adhered to. Following from the principle, it is expected that prior to hearing any evidence in court, the members of the jury should start with the presumption that the probability of the defendant being guilty is close to 0%. However, in practice, Weinstein suggests the probability of guilt or innocence is probably much higher than zero. This is true for a number of reasons, namely that the juror would not believe the case could have come to trial had the civil authorities not amassed substantial evidence of guilt and judicial authorities had not deemed their case weak or frivolous. Weinstein suggests that “It is not unlikely that many jurors begin hearing evidence believing that it is roughly 50% probable that the defendant committed the offense charged with the state having the responsibility to drive up this probability.”[6]
To summarise this argument: Jury members may have very low burden of proof thresholds. This is not helped by the abstractness of the concept and differentiating views of legal scholars on what a reasonable threshold should be, including one suggestion of as low as 60%. Add to the fact that jurors often have a pre-trial presumption of guilt of 50%, I think it is plausible that such an individual could decide on a verdict of guilty merely from hearing character evidence alone!
Even, if one thinks that this could be permissible, the next argument deals specifically with why character evidence is not satisfactory evidence.
b. Exposure to a limited reference class of the defendant
The reference class problem refers to the problem of deciding which ‘class’ I should make inferences from. For example, if I want to think about the probability of Hannah failing her Evidence and Objectivity exam, do I consider: The frequency of exam failures pertaining to all students in the previous year’s module; The frequency that Hannah has failed exams in other modules; The frequency that Hannah has received a failing grade on her coursework this semester; Or some completely different reference class altogether, such as Hannah’s frequency of turning up late to big examinations? It is difficult to decide which reference class is most appropriate to use. Jury’s who are presented with reference class data pertaining to character, may not be aware of the implications of the reference class problem, causing them to apply undue or unfair weight to the evidence presented to them.
Empirical data in the form of recidivism rates, for example, could potentially alter conceptions of prior probability significantly. Recidivism is the continued, habitual or compulsive relapse into undesirable patterns of behaviour. In other words, it is describes the behaviour of repeat offenders. I argued that if jurors had access to information on the ‘reference class’ of a defendant, their knowledge of prior probability of guilt on this information alone would significantly affect their confidence of guilt or innocence. However, recidivism rates are weak evidence in the sense that it could be presented that x percentage of felons will commit the same crime again during their lifetime. However, it may be the case that this percentage is an aggregate, and reoffending is less likely amongst older felons. A better way of presenting this evidence would be to tell the jury thaty is the percentage of felons who reoffend before they reach the defendant’s age group.
However it is easy to imagine that an incorrect reference class can be easily, and either innocently or maliciously, presented. Therefore, there is a huge potential for juries to put undue weight on this type of character evidence if presented with misleading reference class data. It is not surprising then that there is anxiety over reference class based decision-making and that the issue has been flagged in the courts as objectionable.
Shinoubi presents a classic example. Shonubi is a Nigerian citizen who transported illegal heroin by stuffing the heroin-larded paste into balloons, and then swallowing the balloons. He was arrested at JFK airport in New York and tried in the district court presided over by Judge Weinstein. There was reason to suspect that Shonubi had made eight trips in total, although he was only tried for the trip on which he was caught. This was significant, as Weinstein decided the suitable punishment for Shonubi based on the amount of heroin imported illegally. Weinstein used information known about ‘other drug-smuggling balloon swallowing Nigerians’ as a reference class for drawing inferences about Shonubi and sentenced him to a more lengthy spell of incarceration than would otherwise be allowed. [7]
This reliance on a reference class was later deemed unjustified in an appeal court. Re-iterating the anxiety with this approach, the problem with relying on reference class to determine a priori probability of guilt is that, Colyvan et al point out, “Shonubi is a member of many (in fact infinitely many) reference classes; some of these classes consist largely of unsavory types while others consist largely of saints.”[8] Judge Weinstein had assumed that Shonubi was no different to his ‘peers’ and thus had convicted him without knowing which other reference classes he may have belonged. If a judge, and legal scholar, can be so narrowly focused on a singular reference class then it is not a stretch to suggest that a jury made up of ordinary members of the public could make similar assumptions. We can now see that, when presented with evidence of a character, the problem of reference class assigning can be alarmingly prejudicial.
Grounds for Inclusion of Character Evidence
The two charges presented above rightly identify some of the issues with including character evidence in trials. However, I will now respond with three short rebuttals, which serve to show that is possible to mitigate the possibility of jurors apportioning disproportionate weight to character evidence.
c. Uncertainty over burden of proof threshold- Rebuttal
In section a., it was shown that there was some shortcomings to the consensus on high should the burden of proof be and that a low burden of proof threshold could, in a sense, amplify the effect of character evidence. To mitigate this, we must simply insist on jurors that they exercise a high proof-beyond-reasonable-doubt threshold.
It is argued that the law tilts in favour of defendants; it prefers that some guilty go free rather than that some innocents be convicted.[9] In other words, a low false positive rate is more desirable than a low false negative rate in the legal realm. This suggests that a quite high burden of proof is desirable in any society that holds that particular value, as to protect the innocent from being incorrectly convicted. However, it is difficult to pin down exactly how high to push that threshold. The inclusion of character evidence, can be non-toxic, if the burden of proof is high enough so that character evidence cannot stand on its own as the basis for a conviction.
A fair assumption is that the majority of stakeholders in our systems of justice have a desire not to have questions of guilt or innocence decided prematurely, where premature decisions could conclude in a way that might cause undue public controversy. The remedy for this is for judges to adequately convey to the jury members what their burden of proof is, whether it is to be 99%, 90%, 80%, or whatever percentage, to be convinced. Secondly the Jury could go through a pre-trial training and assessment to confirm that they do not fall into the category of individuals who only need to be, for instance, 30% convinced of guilt to convict.
A series of comments on the matter recently appeared in the Journal of Law, Probability, and Risk. Franklin suggested, “any probability less than 0.8 should be declared less than proof beyond reasonable doubt in all circumstances.”[10] Weinstein stated that, “In my opinion, a probability of guilt of no less than 95% should be necessary to support a conviction.”[11] Tillers and Gottfried give a similar appraisal and provide allow that a jury should be permitted to condemn a defendant “only if the juror believes that there is more than a 95% chance that the defendant is guilty.”[12] Perhaps a consultation paper that brought together the views of all legal scholars in a district could be compiled that would then be used as a basis for giving jurors clear guidance on what proof threshold they should exercise.
d. Exposure to a limited reference class of the defendant - Rebuttal
The use of reference classes as a basis for establishing guilt should be admissible in court. Franklin points out that the fact that 99% of drivers cut a particular corner cannot stand as evidence in a court of law that a particular driver cut that corner at a particular time in question. Franklin argues that it is ‘absurd’ that this is inadmissible evidence, as this constitutes logically relevant evidence! [13] Weinstein agrees with Franklin, signalling that he finds it difficult to comprehend why juries are prohibited from considering such easily quantifiable, empirical research on recidivism rates.[14]
In terms of mitigation of the reference class problem: firstly, judges could use their discretion and many years of legal experience to throw-out arguments that appeal to unconvincing or too narrowly defined reference classes; and secondly, it is the prerogative of the defendant’s barrister to present a reference class that shows his client in a good light, therefore balancing the prosecution’s use of reference class data as character evidence.
Conclusion
The inclusion of character evidence has probative value. The reasons for excluding it from trials rely on pragmatic concerns: namely, that jurors may put too much weight on this type of evidence. I have argued that these concerns can be mitigated. Therefore, I conclude that character evidence should be included in legal trials.
[1] I will not directly defend this assumption of probative value of character evidence in this essay.
[2] Kahneman, D., Slovic, P., & Tversky, A., “Judgment under Uncertainty: Heuristics and Biases”, Cambridge: Cambridge University Press, (1982)
[3] Gottdiener, M., “Life in the Air: Surviving The New Culture of Air Travel”, Lanham, MD: Rowman & Littlefield Publishers, (2001), pg. 2
[4] Anderson T., Shum, D.A., Twinning, W.L., & Twinning, W., “Analysis of Evidence – 2nd Ed.”, Cambridge: Cambridge University Press, (2005)
[5] Glendinning, P., “View from the Pennines: Beyond A Reasonable Doubt”, Mathematics Today, Vol. 45, (2009)
[6] Weinstein, J.B. &Dewsbury, I., “Comment On The Meaning Of ‘Proof Beyond A Reasonable Doubt’”, Journal of Law, Probability and Risk, Vol. 5, No. 2, (2006)
[7] Tillers, P., “United States v. Shonubi: A Statistical Oddity?”, Cardozo Law Review, Vol. 18, (1997)
[8] Colyvan, M., Regan, H.M., & Ferson, S., “Is It a Crime to Belong to a Reference Class?”, Journal of Political Philosophy, Vol. 9, No. 2, (2001)
[9] Weinstein, J.B. &Dewsbury, I., “Comment On The Meaning Of ‘Proof Beyond A Reasonable Doubt’”, Journal of Law, Probability and Risk, Vol. 5, No. 2, (2006)
[10] Franklin, J., “Case Comment—United States V. Copeland, 369 F. Supp. 2d 275 (EDNY 2005): Quantification Of The ‘Proof Beyond Reasonable Doubt’ Standard”, Journal of Law, Probability and Risk, Vol. 5, No. 2, (2006)
[11] Weinstein, J.B. &Dewsbury, I., “Comment On The Meaning Of ‘Proof Beyond A Reasonable Doubt’”, Journal of Law, Probability and Risk, Vol. 5, No. 2, (2006)
[12] see Ibid.
[13] Franklin, J., “Case Comment—United States V. Copeland, 369 F. Supp. 2d 275 (EDNY 2005): Quantification Of The ‘Proof Beyond Reasonable Doubt’ Standard”, Journal of Law, Probability and Risk, Vol. 5, No. 2, (2006)
[14] Weinstein, J.B. &Dewsbury, I., “Comment On The Meaning Of ‘Proof Beyond A Reasonable Doubt’”, Journal of Law, Probability and Risk, Vol. 5, No. 2, (2006)
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