Cognitive Bias in Forensic Document Examination

Cognitive Bias in Forensic Document Examination

Cognitive bias is a form of error in thinking which occurs during the process of information processing and interpretation. They are as a result of the person’s attempt to simplify the process of information processing. Ideally, cognitive biases are rules of thumbs that aid people in making sense of the world around them and thereby making decisions with relative speed. In most instances, these decisions will trip one into thinking their decisions were logical thus arriving at weak decisions and poor judgments. Ultimately, the person making the decisions thinks that he/she is objective in their task of evaluating the information available about the world around them. This thinking is however far from the truth since the judgments and decisions are often clogged with errors resulting from these biases (Found & Ganas, 2013, pp 156).

While this process of cognitive bias is natural and occurs within people almost unconsciously, one should be keen in their judgments to avoid such biases when making decisions. In essence, the brain, although remarkable and powerful, is subject to the limitations occasioned by cognitive biases. Forensic experts involved in the examination of documents are at a higher probability of making misinformed decisions due to the implication of cognitive biases. In the process of examining documents and in studying the handwriting patterns, forensic examiners are bound to make errors arising from cognitive biases. In fact, there are hundreds of cases in history in which cognitive bias swayed the testimony of handwriting experts. While the cases from these experts are in no way isolated from the rest, they form an important case study due to their ability to influence judgment, in some cases even unfairly. A mere error from cognitive bias is enough to either implicate an accused wrongly or release an accused unfairly as well (Dyer et al., 2006, pp 1398).

One way through which document examiners can exhibit cognitive bias in the process of their examination is when they focus on a particular aspect in the analysis. For instance, the familiarity of words or even letters may lead to an examiner failing to observe other prominent features such as the writing features. In this manner, the examiner is oblivious of the difference between handwritten items that appear almost similar. The same bias can lead to the examiner not noticing differences between two nor more sets of signatures within the text (Stoel et al., 2014, pp 96). The examiner therefore ends up being influenced by reading individual words and letters and subconsciously fails to have an objective view of the other prominent writing features.

Another bias that may impede an examiners logical judgment is the confirmation bias. In the course of one’s examination, they may be prone to believing and building on the opinion of fellow examiners who usually agree with their opinion (Gianelli, 2010, pp 57). The same examiner may also put off other suggestions that may be proffered by examiners they do not usually agree with. The bias on the individual giving the opinion may influence the leads that the examiner follows in the course of their examination. In this regard, the examiner may for instance, not follow a suggestion that the signatures in a text could be forged simply because it was proposed by an examiner they do not agree. In retrospect, the examiner may decide to follow a misleading suggestion that the patterns are not similar just because a compatriot they agree with suggested the same. This pattern of disillusioned decision making may lead to the collapse of a case just from the cognitive bias from the examiner.

An examiner’s over-reliance on past events may also clog their ability to make logical judgments by their mere belief that certain circumstances lead to specific outcomes. The expert may have certain pre-perceived perceptions about particular cases and that may lead them to assuming that the same outcomes must be achieved faced with similar circumstances. The examiner, in so doing assumes an important rule that every outcome has an equal chance of occurrence and should be tested independent of previous outcomes (Kassin et al., 2013, pp 49). The examiner may for example have the notion that cases of bank fraud always have signatures that are forged. This bias may lead the expert to not consider the writing features and the pattern of words in making their analysis. In this regard, the expert may expect to achieve certain outcomes thereby end up following leads that drive towards these outcomes.

An examiner’s desire to stay consistent with their findings and that of avoiding cognitive dissonance may lead them to make errors in their judgment. These experts may want their findings to always follow a certain path that is consistent with their beliefs. For instance, an examiner may always want to unravel a case of fraud and will work to make sure that it turns out that the case was a fraud one. In this manner, the examiner starts their assessment with a biased concept that the case they are handling involves fraud. In doing so, the examiner may want to convince their mind that all pointers show that the case they are analyzing involves fraud and therefore not entertain any other possibilities. The examiner will then find evidence that obviously points to the fact that the case involves fraud and will be blind to any other option (Koppl, 2005, pp 276).

There is also a possibility of cognitive bias whenever an examiner notices a lead that they do not usually notice. Just like when one purchases a car and you end up noticing very many of the same type of car on the road, the examiner may end up seeing just that lead and avoiding the others. The effect of this bias is that the examiner’s mind becomes attracted to this lead to the point of excitement. For instance, when the examiner does not normally come across forged signatures in court documents, they may be made to believe that it is the only possibility when they come across one that is forged. The reason for the frequent occurrence of the lead is not that others are not appearing, but because the examiner has set it in their mind thereby noticing it more often. Ideally, the examiner’s mind becomes blind to other possible outcomes (Dror, et al., 2006, pp 77). The ability of the expert to explore other leads and possibilities is in effect clogged by this bias.

The examiner’s perception of how the world is may also be a source of cognitive bias in the course of their analysis. For instance, an examiner who believes that Muslims cannot steal money from the poor may be forced to make judgments that reflect the same. In their assessment of documents, they may assume that the case cannot be a fraudulent one simply because the accused is a Muslim. These perceptions about how the world is make the examiner afraid of any change to this belief and are always desirous of confirming their beliefs of the world to be true. The result is that these examiners end up following only the leads that do not have the probability of contradicting their views of the world.

Most examiners, as do most people do, tend to pay more attention to the outcomes that things will turn out to be negative. This ideology stems from man’s selective attention and their perceptions that negative will always occur (Saks et al., 2003, pp 86). Examiners do share in this form of cognitive bias leading to absurd judgments. A document examiner may have a notion of things not always being right and having the suspicion that the accused is wrong. In effect, the expert ends up exploring evidence that castigates the accused just to prove their theory of the accused being on the wrong. This form of bias is particularly detrimental as it may lead to false detentions of the accused even when they are not guilty. The examiner’s mind is biased and in their desire to take shortcuts in decision making, they end up not exploring possibilities of the accused being innocent. In their minds, the accused is guilty and their job is only to prove the same and warrant a conviction. The examiners therefore end up following leads that point to the guilt of the accused all along their examination.

Every human is accustomed to always wanting to go with the flow of the public. The document examiners are not spared in having this limitation and they at times find themselves flowing with the crowd or the public mood. In cases of big public cases involving corruption for example, the examiner may find themselves taking sides and following the chanting of the public. If, for instance, the general public believes that money from their treasury was fraudulent stolen by their leaders, the examiner may end up believing the same thing (Dror et al., 2006, pp 73). They may end up subconsciously and unconsciously trying to prove the same accusations and therefore having a bias in their analysis. The result is that they turn out to favor a certain side of the story and find only evidence that supports such outcomes. The result is the culmination of flawed judgments and poor decisions that may taint the credibility of the said examiners in ad light.

Another form of bias that examiners in forensic document analysis are faced with is the anchoring effect. This occurs when an examiner limits the possibility of outcomes to a set of outcomes that they have set themselves. They may then end up comparing and contrasting other outcomes based on the outcomes that they have set in advance. The examiners then end up believing that one of the two outcomes must be the rue one and therefore choose the one that is most probable to occur. For example, an expert may be hard-pressed to believe that a case may either have a forged signature or forged name of the person authorizing a certain transaction. The examiner will then weigh out the one that has more evidence and presume that to be the case. In truth, however, the outcome may not even involve either of the set limited outcomes leave alone it being one of them.

Ideally, none of the experts involved in forensic document analysis would want to believe that their judgments are biased. However, it is there in truth and the only way to correct it is in identifying it first. An expert’s ability to recognize an influence from bias and their skills in overcoming the biases are integral to their credibility (Found & Ganas, 2013, pp 155). In fact, having a cognitive bias is not wrong, but not identifying and correcting it is what is detrimental. The fact that these experts are trained in applying analytical methods to make opinions may in itself be a source of bias due to the inclination towards prior experiences on their part. Forensic document examiners as well as other experts must be able to recognize when cognitive bias either from self or from others is influencing their judgments and decisions.

One way of reducing cognitive bias is the use of the Fischoff Method that involves the Upside down comparison of texts in a document. The habit of comparing known and question signatures and handwriting can provide insights on inconsistencies. By so doing, the examiner eradicates the possibility of being subconsciously influenced by the bias of reading individual words and letters. The action of putting the document in an upside down position gives the examiner a more objective view of other features that are prominent in the text such as inconsistencies between two sets of signatures. The method is effective in countering observer effects of familiar word and letter constructs that are related.

Another de-biasing technique involves the use of sequential unmasking (Koppl, 2005, pp 279) in case management. The process involves two steps that work towards reducing the potential for bias. The first step is the filtration of the information that is domain-irrelevant. This information is first identified and then quarantined to avoid the chance of the same affecting the judgment of the examiner. The second step involves the release or sifting of domain relevant information to allow for the exclusive analysis of the relevant information. As thus, the examiner is free of bias that could have been occasioned by domain-irrelevant information. The outcome of an expert’s analysis is therefore not influenced by this form of bias and the evaluation of evidence becomes credible for the expert to use.

Another way of reducing cognitive bias, and indeed other biases, in the forensic profession would be to standardize proper procedures and protocols. In addition, the document examiners should be trained on how to minimize and deal with biases. Ideally having bias is not an unethical thing as it results from the very processes that occur in the brain. As thus, bias cannot therefore be wished away or turned off by the mere willpower of awareness. Nevertheless, proper training of the document experts by cognitive experts could contribute in the reduction and minimization of bias in document examination (Koppl, 2005, pp 274).

Documents being studied should also be studied before observation of the reference documents to guard against confirmation bias. Where there exists more than one document that are thought to be one similar copy, they ought to be studied in an orderly manner such that the one believed to be worst starts. This procedure can also avoid confirmation bias between the many documents under study. Moreover, there should be independent assessment of the documents such that the identity of the initial examiner is concealed from the subsequent ones.

The use of statistical approach in evaluating documents is also recommended to avoid reliance on an examiner’s experience. Moreover, a completely independent examiner may be introduced to repeat an examiner’s process and not being given any contextual information. This procedure ensures that most biases are eliminated and can be a useful learning process for the examiners (Saks et al., 2003, pp 88). They can for instance identify the areas and scenarios where they may have been influenced by bias in coming up with decisions.



DYER, A.G., FOUND, B. and ROGERS, D., 2006. Visual attention and expertise for forensic signature analysis. Journal of forensic sciences, 51(6), pp. 1397-1404

FOUND, B. and GANAS, J., 2013. The management of domain irrelevant context information in forensic handwriting examination casework. Science & Justice, 53(2), pp. 154-158

STOEL, R.D., DROR, I.E. and MILLER, L.S., 2014. Bias among forensic document examiners: Still a need for procedural changes. Australian Journal of Forensic Sciences, 46(1), pp. 91-97

Giannelli, P. C., 2010. Cognitive bias in forensic science. Criminal Justice,  61(1), pp.54-59

Kassin, S. M., Dror, I. E., & Kukucka, J., 2013. The forensic confirmation bias: Problems, perspectives, and proposed solutions. Journal of Applied Research in Memory and Cognition, 2(1), pp. 42-52

Koppl, R., 2005. How to improve forensic science. European Journal of Law and Economics, 20(3), pp. 255-286.

Dror, I. E., Charlton, D., & Péron, A. E., 2006. Contextual information renders experts vulnerable to making erroneous identifications. Forensic science international, 156(1), pp. 74-78.

Saks, M. J., Risinger, D. M., Rosenthal, R., & Thompson, W. C., 2003. Context effects in forensic science: a review and application of the science of science to crime laboratory practice in the United States. Science & Justice, 43(2), pp. 77-90.

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