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  • Terry Elmaleh

Being Aware of Cognitive Bias, and most especially Blind Spot Bias

It is essential that the Forensic Handwriting Examiner is aware of the types of biases that she can be prone to which could compromise not only the validity and reliability of an examination; but also result in fundamental errors in the forming of opinions and conclusions. Using the human element perspective to dissect forensic science is not a simple task and is called Cognitive Forensics.

One of these biases is Blind Spot Bias – This is when an examiner fails to recognise her own cognitive and motivational biases. People recognise bias more in others than they do in themselves.

The examiner needs to ensure that she is metacognitively aware of her potential biases. Specifically she should be aware and understand her own thought processes whilst performing her work. She needs to be aware of how she thinks about thinking.

Cognitive bias is the process of acquiring knowledge by the use of reasoning, intuition, or perception and it takes many forms. These are additional types of cognitive bias that forensic handwriting examiners should be aware of:

  • Confirmation Bias: One of the longest recognised and most pervasive forms of bias occurs when an examiner focuses on the information that confirms the client’s position and then becomes receptive to it. This occurs when the examiner forms a hypothesis or belief and uses the information to confirm that belief in her opinions and conclusions. This is a tendency to make the evidence consistent with the “known” (or believed) facts. (Michael Allen, 2016).

  • Anchoring Bias: This bias occurs when we are over-reliant on the first piece of information that we receive which could be our client’s account of the situation.

  • Availability Heuristic Bias: This is an overestimation of the importance of information and bias that you already have when evaluating handwriting.

  • Bandwagon Bias: This bias occurs when one examiner agrees with another’s opinion and is especially a risk factor when one handwriting examiner assesses another’s work. This is to be avoided by ensuring an independent examination of each case prior to critiquing a colleague’s report.

  • Choice-Support Bias: The decision to evaluate and analyse certain features as opposed to others in a handwriting sample can lead to a handwriting examiner feeling positive about her findings even if her choice had fundamental flaws.

  • Conservatism Bias: This bias occurs when an examiner is faced with new evidence which she finds difficult to accept and favours the information that was initially given to her. All information has to be given equal weight in all analyses and examinations. This is linked to Ostrich Bias where the examiner ignores information that may be in opposition or negate her original opinion.

  • Overconfidence: An opinion can be jeopardised should a handwriting examiner be convinced that she is right and overconfident about her abilities. The same professional standards, processes and procedures should be adhered to throughout the examination no matter how certain the examiner is of her capabilities.

  • Selection Bias: This occurs when the samples of handwriting included in the study are not truly representative of the person’s handwriting. This can happen because there were not enough samples for comparison.

  • Stereotyping: This bias takes place when an examiner allows pre-conditioned ideas that have no scientific basis influence her in reaching an opinion.

  • Reporting bias: This is seen when facts that do not support the client’s position are not taken into account or not analysed or reported.

To minimize any cognitive bias, handwriting examiners must continually ensure that they do not perform their work selectively in their client’s favour or under pressure from a client to give an anticipated or required opinion. The examiner should reassess impressions of information and challenge her pre-existing assumptions and hypotheses to avoid coming to any pre-conceived conclusions. Any background information that is necessary for the handwriting examiner to be aware of before beginning the handwriting examination should not influence the opinion reached.

In addition to being aware of these types of bias the forensic handwriting examiner should follow well-established processes and procedures and observe ethical guidelines at all times.


  • Allen M. 2016 Foundations of Forensic Document Analysis, Theory and Practice, West Sussex, John Wiley & Sons Ltd

  • Brycz. B, Wyszomirska-Gora M, Bar-Tal Y, Wisniewski P., 2014, The effect of metacognitive self on confirmation bias revealed in relation to community and competence: Polish Psychological Bulletin, Vol 45, Issue 3

  • Dror I.E. 2015 Cognitive Neuroscience in Forensic Science: Understanding and utilising the human element. Phil. Trans. R. Soc. B 370: 20140255

  • Rosa C. (PhD) 2016 Forensic Handwriting Examination

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