Matthew B. Thompson

Identifying Fingerprint Expertise

“CSI”-style TV shows give the impression that fingerprint identification is fully automated. In reality, when a fingerprint is found at a crime scene, it is a human examiner who is faced with the task of identifying the person who left the print—a task that falls squarely in the domain of psychology. The difficulty is that no properly controlled experiments have been conducted on fingerprint examiners’ accuracy in identifying perpetrators (Loftus & Cole, 2004), even though fingerprints have been used in criminal courts for more than 100 years. Examiners have even claimed to be infallible (Federal Bureau of Investigation, 1984). However, the U.S. National Academy of Sciences has recently condemned these claims as scientifically implausible, reporting that faulty analyses may be contributing to wrongful convictions of innocent people (National Research Council, Committee on Identifying the Needs of the Forensic Science Community, 2009). Proficiency tests of fingerprint examiners and previous studies of examiners’ performance have not adequately addressed the issue of accuracy, and they been heavily criticized for (among other things) failing to include large, counterbalanced samples of targets and distractors for which the ground truth is known (see Cole, 2008, and Vokey, Tangen, & Cole, 2009). Thus, it is not clear what these tests say about the proficiency of fingerprint examiners, if they say anything at all. Researchers at the National Academy of Sciences and elsewhere (e.g., Saks & Koehler, 2005; Spinney, 2010) have argued that there is an urgent need to develop objective measures of accuracy in fingerprint identification. Here we present such data.

Expertise in Fingerprint Identification

Although fingerprint experts have presented evidence in criminal courts for more than a century, there have been few scientific investigations of the human capacity to discriminate these patterns. A recent latent print matching experiment shows that qualified, court‐practicing fingerprint experts are exceedingly accurate (and more conservative) compared with novices, but they do make errors. Here, a rationale for the design of this experiment is provided. We argue that fidelity, generalizability, and control must be balanced to answer important research questions; that the proficiency and competence of fingerprint examiners are best determined when experiments include highly similar print pairs, in a signal detection paradigm, where the ground truth is known; and that inferring from this experiment the statement “The error rate of fingerprint identification is 0.68%” would be unjustified. In closing, the ramifications of these findings for the future psychological study of forensic expertise and the implications for expert testimony and public policy are considered.

The nature of expertise in fingerprint matching: Experts can do a lot with a little

Expert decision making often seems impressive, even miraculous. People with genuine expertise in a particular domain can perform quickly and accurately, and with little information. In the series of experiments presented here, we manipulate the amount of “information” available to a group of experts whose job it is to identify the source of crime scene fingerprints. In Experiment 1, we reduced the amount of information available to experts by inverting fingerprint pairs and adding visual noise. There was no evidence for an inversion effect—experts were just as accurate for inverted prints as they were for upright prints—but expert performance with artificially noisy prints was impressive. In Experiment 2, we separated matching and nonmatching print pairs in time. Experts were conservative, but they were still able to discriminate pairs of fingerprints that were separated by five-seconds, even though the task was quite different from their everyday experience. In Experiment 3, we separated the print pairs further in time to test the long-term memory of experts compared to novices. Long-term recognition memory for experts and novices was the same, with both performing around chance. In Experiment 4, we presented pairs of fingerprints quickly to experts and novices in a matching task. Experts were more accurate than novices, particularly for similar nonmatching pairs, and experts were generally more accurate when they had more time. It is clear that experts can match prints accurately when there is reduced visual information, reduced opportunity for direct comparison, and reduced time to engage in deliberate reasoning. These findings suggest that non-analytic processing accounts for a substantial portion of the variance in expert fingerprint matching accuracy. Our conclusion is at odds with general wisdom in fingerprint identification practice and formal training, and at odds with the claims and explanations that are offered in court during expert testimony.

Model forensic science

This article provides an explanation of the duties and responsibilities owed by forensic practitioners (and other expert witnesses) when preparing for and presenting evidence in criminal proceedings. It is written in the shadow of reports by the National Academy of Sciences (US), the National Institute of Standards and Technology (US), the Scottish Fingerprint Inquiry and a recent publication entitled ‘How to cross-examine forensic scientists: A guide for Lawyers’. The article examines potential responses to questions focused on the need for scientific research, validation, uncertainties, limitations and error, contextual bias and the way expert opinions are expressed in reports and oral testimony. Responses and the discussion is developed around thematics such as disclosure, transparency, epistemic modesty and impartiality derived from modern admissibility and procedure rules, codes of conduct, ethical and professional responsibilities and employment contracts. The article explains why forensic practitioners must respond to the rules and expectations of adversarial legal institutions. Simultaneously, in line with accusatorial principles, it suggests that forensic practitioners employed by the state ought to conduct themselves as model forensic scientists.

Multisensory Integration With a Head-Mounted Display: Sound Delivery and Self-Motion

Objective: We tested whether the method of sound delivery affects peoples ability to integrate information from multiple modalities when they are walking and using a head-mounted display (HMD). Background: HMDs increasingly support mobile work. Human operators may benefit from auditory support when using an HMD. However, it is unclear whether sound is better delivered publicly in free field or privately via earpiece and what the effect of walking is. Method: Participants identified mismatches between sounds and visual information on an HMD. Participants heard the sounds via either earpiece or free field while they either sat or walked about the test room. Results: When using an earpiece, participants performed the mismatch task equally well whether sitting or walking, but when using free-field sound, participants performed the task significantly worse when walking than when sitting (p = .006). Conclusion: The worse performance for participants using free-field sound while walking may relate to spatial and motion inconsistencies between visual events on the head-referenced HMD and auditory events from world-referenced speakers. Researchers should more frequently examine the effect of self-motion on peoples ability to perform various multisensory tasks. Application: When multisensory integration tasks are performed with an HMD and free-field delivery of sound, as may happen in medicine, transportation, or industry, performance may suffer when the relative location of sound changes as the user moves.

Human matching performance of genuine crime scene latent fingerprints

There has been very little research into the nature and development of fingerprint matching expertise. Here we present the results of an experiment testing the claimed matching expertise of fingerprint examiners. Expert (n = 37), intermediate trainee (n = 8), new trainee (n = 9), and novice (n = 37) participants performed a fingerprint discrimination task involving genuine crime scene latent fingerprints, their matches, and highly similar distractors, in a signal detection paradigm. Results show that qualified, court-practicing fingerprint experts were exceedingly accurate compared with novices. Experts showed a conservative response bias, tending to err on the side of caution by making more errors of the sort that could allow a guilty person to escape detection than errors of the sort that could falsely incriminate an innocent person. The superior performance of experts was not simply a function of their ability to match prints, per se, but a result of their ability to identify the highly similar, but nonmatching fingerprints as such. Comparing these results with previous experiments, experts were even more conservative in their decision making when dealing with these genuine crime scene prints than when dealing with simulated crime scene prints, and this conservatism made them relatively less accurate overall. Intermediate trainees-despite their lack of qualification and average 3.5 years experience-performed about as accurately as qualified experts who had an average 17.5 years experience. New trainees-despite their 5-week, full-time training course or their 6 months experience-were not any better than novices at discriminating matching and similar nonmatching prints, they were just more conservative. Further research is required to determine the precise nature of fingerprint matching expertise and the factors that influence performance. The findings of this representative, lab-based experiment may have implications for the way fingerprint examiners testify in court, but what the findings mean for reasoning about expert performance in the wild is an open, empirical, and epistemological question.

Thinking forensics: cognitive science for forensic practitioners

Human factors and their implications for forensic science have attracted increasing levels of interest across criminal justice communities in recent years. Initial interest centred on cognitive biases, but has since expanded such that knowledge from psychology and cognitive science is slowly infiltrating forensic practices more broadly. This article highlights a series of important findings and insights of relevance to forensic practitioners. These include research on human perception, memory, context information, expertise, decision-making, communication, experience, verification, confidence, and feedback. The aim of this article is to sensitise forensic practitioners (and lawyers and judges) to a range of potentially significant issues, and encourage them to engage with research in these domains so that they may adapt procedures to improve performance, mitigate risks and reduce errors. Doing so will reduce the divide between forensic practitioners and research scientists as well as improve the value and utility of forensic science evidence.

Multisensory Integration With a Head-Mounted Display: Background Visual Motion and Sound Motion

Objective: The aim of this study was to assess how background visual motion and the relative movement of sound affect a head-mounted display (HMD) wearer’s performance at a task requiring integration of auditory and visual information. Background: HMD users are often mobile. A commercially available speaker in a fixed location delivers auditory information affordably to the HMD user. However, previous research has shown that mobile HMD users perform poorly at tasks that require integration of visual and auditory information when sound comes from a free-field speaker. The specific cause of the poor task performance is unknown. Method: Participants counted audiovisual events that required integration of sounds delivered via a free-field speaker and vision on an HMD. Participants completed the task while either walking around a room, sitting in the room, or sitting inside a mobile room that allowed separate manipulation of background visual motion and speaker motion. Results: Participants’ accuracy at counting target audiovisual events was worse when participants were walking than when sitting at a desk, p = .032. Compared with when they were sitting at a desk, participants’ accuracy at counting target audiovisual events showed a trend to be worse when they experienced a combination of background visual motion and the relative movement of sound, p = .058. Conclusion: Multisensory integration performance is least effective when HMD users experience a combination of background visual motion and relative movement of sound. Eye reflexes may play an important role. Application: Results apply to situations in which HMD wearers are mobile when receiving multimodal information, as in health care and military contexts.

Flashed Face Distortion Effect: Grotesque Faces from Relative Spaces

We describe a novel face distortion effect resulting from the fast-paced presentation of eye-aligned faces. When cycling through the faces on a computer screen, each face seems to become a caricature of itself and some faces appear highly deformed, even grotesque. The degree of distortion is greatest for faces that deviate from the others in the set on a particular dimension (eg if a person has a large forehead, it looks particularly large). This new method of image presentation, based on alignment and speed, could provide a useful tool for investigating contrastive distortion effects and face adaptation.

Multisensory integration with a head-mounted display: role of mental and manual load.

Objective: The aim of this study was to replicate the finding that multisensory integration with a head-mounted display (HMD) is particularly difficult when a person is walking and hearing sound from a free-field speaker, and to extend the finding with a response method intended to reduce workload. Background: HMDs can support the information needs of workers whose work requires mobility, but some low-cost solutions for delivering auditory information may be less effective than others. Method: For the study, 24 participants detected whether shapes moving on the HMD screen made a sound appropriate to their forms when they collided with other shapes. Independent variables were self-motion (participants were mobile or seated), sound delivery (free-field speakers or an earpiece), and response method (noting mismatches via a mental count or via a manual clicker). Results: Unexpectedly, overall mismatch task accuracy was worse with the clicker (p = .027) than without. Participants also reported that it was harder to time-share the mismatch task with clicker responses (p = .033). In the clicker condition, self-motion and sound delivery interacted but in the opposite direction to the previous study. Conclusion: The best way of delivering auditory information to mobile workers performing a multisensory integration task with an HMD may depend on whether responding involves mental load or manual load. Broader theories are needed to capture factors influencing performance. Application: Until more powerful theory is developed, designers should perform careful formative and summative tests of whether the activities to be performed by mobile HMD wearers will make some sound delivery solutions less effective than others.