Chapter 4 An investigation of self-reported fingermark quality assessment decision rationale
4.6.1. Objectives 4.1 and 4.2: Practitioner fingermark submission making self-reported
Consideration of low level responses
A broad range of rationale for fingermark submission decisions (categorised as decision factors) were exhibited by practitioners within both Laboratory A and the MPS Laboratory, with a total of 93 different decision factors reported (16 unique to Lab A, 41 unique to MPS lab, and 36 reported within both laboratories). The Grounded Theory style analysis employed ensured that each of these decision factors was extracted from the data prior to grouping them at a higher level. This meant that the whole spectrum of reasons for mark submission decision making could be considered. Some of the lesser
Page | 153 reported decision factors may help to explore the thought processes surrounding mark submission for particular practitioners. The decision category ‘Presentation could make a difference’ contains three such interesting decision factors which shed light upon aspects of the mark submission process. ‘Could be tweaked to get better contrast’ is a decision factor reported by practitioners in both Laboratory A and the MPS Laboratory, this suggests an acknowledgment of the importance of imaging processes within mark submission. It could be considered that, as fingermark submission decision making occurs prior to fingermark image capture during laboratory workflow, the influence of the imaging process on the final fingermark to be submitted to the bureau is of key importance. Further research to empirically establish the effects of imaging processes on fingermark quality is therefore an important step to fully understanding the requirements of the practitioner submission decision. The decision factor ‘better without a glass on’ also alludes to the differences in the appearance of the mark according to the mechanism of viewing it. The factor ‘expert may be able to see more’ is also included within this category. This factor is interesting as it demonstrates that practitioners are considering differences in expertise between themselves and fingerprint examiners. This relationship in relation to the quantity of information within a fingermark will be further investigated in Chapter 5 of this thesis.
Practitioners within the MPS Laboratory refer to both ‘unusual pattern’ types and ‘common pattern types’ in their decision rationale, suggesting a preference for submitting rare pattern types for comparison. Whilst it is indeed the case that a rare pattern type may be easier to identify by an examiner, it is not the case necessarily that this identification is more valuable than an identification made in relation to a common pattern. It is also the case that there are differences in the commonality of fingerprint patterns across different populations (Kanchan & Chattopadhyay, 2006, Nanakorn et al., 2013, and Stamboulie et al., 2015), so basing a submission decision on the perceived commonality of a pattern type may not be an effective submission decision mechanism if used in isolation.
One decision factor provided during the experimental task wasthe use of ‘gut instinct’ during mark submission decision making. Whilst this may, perhaps, appear to be a non-scientific and worrying reason for determining whether or not to submit a fingermark, it may actually be, a very honest and helpful decision rationale and an accurate explanation of the decision process; using intuition to make a submission decision. Indeed, the use of intuition in decision making is not necessarily a negative concept. Dane et al. (2012) found that the effectiveness of intuition in analytical thought is increased with increased domain experience. The decision factor of ‘gut instinct’ could also suggest a lack of metacognitive awareness (knowledge of cognition) in the submission decision. Research has suggested that human expert decision makers often have limited metacognition and that some
Page | 154 cognitive activities are inaccessible to metacognition (Nisbett & Wilson, 1977). Metacognition of cognitive processes has been shown to be of benefit to decision making (Batha & Carroll, 2007). However, Hochberg (2014) linked increased metacognitive awareness to decreased diagnostic accuracy in physicians. A high occurrence of ‘no response’ when asked for decision rationale within both laboratories (16% and 27%) may also indicate difficulties in determining the cognitive processes involved. Further evidence for a possible lack of metacognitive ability within the practitioner group is, perhaps, apparent within the 2nd level detail decision category. Commonly reported decision factors
within this category were ‘sufficient’ and ‘insufficient’ detail. Such a broad description of how practitioners had made their submission decision may suggest that they were unaware of the cognitive process that had led then to such a determination of sufficiency or insufficiency, or may, on the other hand, suggest the high importance of a cognitive threshold within the submission decision making process. Newell and Shanks (2014) highlight that metacognition information can be gleaned from participants, however, the open ended question asked to participants in the present study would not meet the sensitivity criteria detailed by Newell and Shanks (ibid). Therefore, there would be merit in extending this piece of qualitative research to further investigate metacognition around fingermark submission in line with the method detailed by Newell and Shanks (ibid).
A high level consideration of decision categories
A higher level comparison of the make-up of decision categories between practitioners within Laboratory A and those within the MPS Laboratory demonstrates a similarity in the types of decision rationale reported. The most commonly occurring rationale within both laboratories is 2nd level detail
(33% of decision factors within Lab A and 34% of decision factors within the MPS Lab), with Clarity (26%, and 11%) and 1st level detail (16% and 20%) also largely represented within both groups. The
largest decision category as a result of rationale provided by Laboratory A (2nd level detail) was further
investigated to examine in more detail the type of decision factors within this category. The decision factors were shown to belong to a number of sub categories relating to different aspects of 2nd level
detail. 78% of factors within this category related to either a numerical value or count of minutiae (number/magnitude of minutiae, or ease of counting minutiae), or suggested a threshold of minutiae being reached (sufficient or insufficient minutiae). Such a predominant reliance on minutiae count in relation to a threshold to determine mark sufficiency for submission is an interesting finding. An example of a minutiae count decision rationale was ‘6+ points present so submit’. This statement clearly expresses the use of the two key components of Signal Detection Theory (Phillips et al., 2001) the detection of minutiae (quality indicators) within the marks, and the implementation of a threshold at which this number represents a mark of sufficient quality for submission. With so many
Page | 155 practitioners describing the use a numerical count of minutiae and the adoption of such a threshold it would seem that minutiae may play a key role in the decision process. Minutiae counts have, historically been of importance within UK fingerprinting. Until it’s abolishment in 2001 (Mackenzie, 2011) fingerprint examiners adopted a 16-point standard meaning that 16 points needed to be consistent between a suspect and exemplar fingerprint for a match to be said to occur. This historical reliance upon the presence of a high number of minutiae in a mark may go some way to explain an apparent reliance on a minutiae count as a mark submission mechanism by practitioners. Indeed, comparing the decision mechanisms of practitioners employed prior to the abolishment of the 16 point standard with those who began practicing after this change would be an interesting extension of this study. It may be that counting minutiae is a way in which the highly subjective task of mark submission (research undertaken within Chapter 3 highlighted that there is no formal procedure or training in relation to determining which marks to submit) can be made more objective. It may be that the objectifying of this decision through the use of a minutiae count is, indeed, an effective strategy for mark submission. Chapter 5 will examine this idea through further empirical study.
Data in relation to inter-practitioner differences in decision rationale demonstrates a representative proportion of the decision categories across the practitioner group. It is not the case that individual practitioners are adopting a consistent rationale for their decisions, for example one practitioner basing all of their decisions on 2nd level detail, whilst another basing all their decisions on mark clarity,
rather that the decision rationale given by each practitioner has varied in different cases. This may have suggested that practitioners were using different mechanisms for decision making according to the experimental mark resulting in a mixed profile of rationale per participant. However, consideration of the mixed make up of decision factors for each experimental mark suggests that this is not the case. The range of decision rationale reported by each practitioner may be an indicator of the high level of subjectivity of the decision making process. It may be that the criteria for mark submission depends upon the most immediate quality indicator within the mark, for example if a pattern is clearly present then that may become the indicator used, instead of looking further at this pattern. On the other hand, it could be the case that the rationale provided do not actually reflect the true rationale for mark submission decision making, and that the submission decision is a subconscious process and that practitioners are actively seeking a rationale to report in the study. This would fit with views of the challenges of metacognitive processes in experts (Nisbett & Wilson, 1977).
An additional consideration is that practitioners may be using multiple cues when making their submission decision. Indeed, many practitioners stated multiple decision factors in relation to the same fingermark, often illustrating an evaluative process such as ‘the clarity is good, but there are
Page | 156 insufficient characteristics present’. It could be that a sequential process of quality indicators is being utilised, for example, making an initial estimation of quality and if this is sufficient moving on to pattern, and then 2nd level detail, and so on. Support for the use of quality indicators (or attributes) in
this way may come from the Decision by Sampling literature which would suggest the comparison of the quality rating of a series of quality attributes against those in working memory (Stewart et al., 2006) (the present experimental design should have ruled out comparison against attributes in the decision context as marks were presented in isolation). The order in which the present marks were presented could, however, have had an effect on the quality attributes held in working memory (in relation to the previously view mark), so the effect of the order of marks on the rationale provided may well be an interesting extension of the present analysis.
It is important to consider that the findings presented with this chapter relate to the decision rationale of practitioners working within two metropolitan UK fingermark enhancement laboratories. Whilst the data represent the rationale of all available practitioners within these laboratories, they do not represent a sample of practitioners from across the breadth of UK laboratories. Due to the varying nature of the structure and working practices of police scientific support departments across the UK and due of the varying nature of crimes typically investigated, it may be the case that differences in approach would be identified by taking a wider practitioner sample. As such, the data cannot be said to be indicative of the decision rationale of practitioners across the UK, rather provides a starting point for further understanding of the fingermark submission decision making process.