A risk-based approach to cognitive bias in forensic science.

Over the past decade, the potential impact of cognitive bias in forensic science has instigated much discussion and debate between academics, scientists and those in the justice sector. Evidence of bias influencing subjective decision-making across a range of forensic disciplines has been described in the literature. Forensic service organisations are being urged to address cognitive bias in subjective decision-making by designing processes or procedures to limit access to (irrelevant) contextual information or reduce dependence on cognitive functions. Although some laboratories have implemented bias mitigating strategies, with varying impact on operational efficiency, there has been no systematic assessment of the risk posed by cognitive bias. Forensic Science SA assessed the potential impact of bias on forensic interpretations across multiple disciplines, using a risk management framework. This process proved useful in assessing the effectiveness of existing bias mitigating strategies and identified the latent level of risk posed. While all forensic organisations should seek to implement bias limiting measures that are simple, cost-effective and do not adversely impact efficiency, using a risk-based approach has contextualised the limited benefit of introducing resource hungry measures, as postulated in the literature. That is not to suggest that forensic organisations should dismiss the potential influence of cognitive bias but they need to strike an appropriate balance between risk and return, as they do with any business risk.

The analysis of dyes in ball point pen inks on single paper fibres using laser desorption ionisation time of flight mass spectrometry (LDI-TOFMS).

An important requisite for the forensic analysis of inks on documents is that damage to the document is avoided or minimised. This paper describes a technique for dye identification in ballpoint pen inks using LDI-TOFMS on single ink bearing paper fibres and its application to a case. A single ink bearing paper fibre can be prised from the surface of the document under a stereo microscope and presented to the instrument for analysis without further treatment. This sampling process causes imperceptible damage to the surface of the document. Clear mass spectrometric identification of the ink dyes is obtained. A case example is provided to illustrate the practical application of the technique.

Forensic document examiners' skill in distinguishing between natural and disguised handwriting behaviors.

Disguised handwriting is problematic for forensic document examiners (FDEs) and attracts higher misleading and inconclusive rates on authorship opinions than does genuine writing (Found B, Rogers D, International Graphonomics Society, 2005). There are currently no published empirical data on FDEs' expertise in distinguishing between natural and disguised writing behavior. This paper reports on the skill of FDEs for determining the writing process of 140 pairs of natural and disguised writings and compares their results with those of a control group of laypeople. A significant difference was found between the examiner and lay group. FDEs' expertise is characterized by their conservatism, where FDEs express a higher proportion of inconclusive opinions (23.1% for FDEs compared to 8.4% for the control group). This leads to the FDEs expressing a smaller percentage of misleading responses when calling writings as either naturally written or disguised (4.3% for FDEs compared with 12.2% for the control group).

Forensic handwriting examiners' opinions on the process of production of disguised and simulated signatures.

Large-scale blind testing of forensic handwriting examiners (FHEs) has shown that authorship opinions on disguised and simulated signatures attract higher misleading and inconclusive rates than genuine signatures do. To test whether this is due to the failure of FHEs to detect the indicators of disguise/simulation behaviours we examined their opinions regarding the 'process of production' (which in this case was a choice between written naturally or written using a disguise/simulation strategy) of the questioned disguised and simulated signatures in blinded skill testing trials. The relationship between their process opinions and authorship opinions is then assessed. It was found that the majority of the inconclusive authorship opinions for both disguised and simulated signatures had a correct process opinion (707 of 1241, 57.0% for disguised; 3838 of 4368, 87.9% for simulated), with only 7.3% (90 of 1241) of the disguised and 0.85% (37 of 4368) of the simulated signatures exhibiting incorrect process opinions. For the total misleading authorship opinions relating to disguised signatures, the majority of the process opinions were correct (167 of 241, 69.3%) indicating that a disguise/simulation process was detected, but misinterpreted as being by another writer. These results show the usefulness of FHEs offering a first stage simulation/disguise process opinion without going on to form an opinion on authorship, as the support for the proposition that a signature is something other than genuine may be, in itself, of strong evidential value.