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Craig Coppock brought us a look at what he defines as "Pattern Interference" in latent print examination.

Cynthia Rennie distills a presentation by Dr. Itel Dror and David Charlton at the recent ABFDE seminar.

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The Effect of Contextual Information / Why Experts Make Errors
Lecture Notes by Cynthia Rennie
Presentation by Dr. Itel Dror and David Charlton

The Effect of Contextual Information

Dr. Itel Dror, researcher at the University of the Southampton School of Psychology, discussed the results of some of the experiments that he and his colleagues have conducted regarding the decision-making process that experts undergo when examining and comparing fingerprints.

In one of his studies, Dr. Dror examined the effect that contextual information might have on the fingerprint examiner. He obtained the cooperation of five fingerprint experts who agreed to take part in the study without knowing exactly when they would be tested. The researchers collected pairs of fingerprints from archives that the each expert had examined and judged approximately five years earlier as a clear and definite match. For the purposes of the study, these very same pairs of fingerprints were re-presented to the same experts, but this time they were told that the pair of prints was the one that was erroneously matched by the FBI as Brandon Mayfield, the accused "Madrid bomber". This created an extraneous context that the prints were a non-match. (The researchers ensured that none of the participants were familiar with the "real" Madrid/Mayfield fingerprints.)
The fingerprint examiners were asked to decide whether there was sufficient information available in the pair of prints to make a definite and sound decision, and, if so, what that decision was - i.e. match or non-match. The examiners were allowed to adjust the magnification and lighting of the prints, and were given as much time as they wanted for the examination. They were also told to ignore the context and background information, and to focus solely on the actual print in their evaluation and decision-making.
Of the five participants, only one remained consistent and judged the prints to be a match. The other four changed their identification decision from the one that they had made five years earlier. Thinking that they were looking at the Mayfield fingerprint, three of the four examiners determined that the two prints were not a match, and the other decided that the prints offered insufficient information to make a definite decision.
The researchers considered several possible reasons for the changes of heart exhibited by the four examiners, including practitioner error; methodological and procedural problems in the way that the examiners were trained and identifications were conducted; and the possibility that the scientific basis of fingerprint identification was flawed. They concluded that the findings of inconsistent identification decisions may reflect cognitive flaws and limitations in conducting objective and independent processing and evaluation of the information. They warn that other extraneous contextual effects (such as emotional context; 'group think'; biases; hopes and expectations; self-fulfilling prophesies and peer pressure) can also have an effect on the examiner.
The report concluded by suggesting that vulnerabilities in fingerprint identification can be minimized by better initial selection and screening of fingerprint examiners; by appropriate training and professional development, and by the adoption of methodological procedures that adequately address potential pitfalls. The fact that one examiner did not change their findings demonstrated to the researchers that it was possible to be objective even in the face of overwhelming contextual information.

Why Experts Make Errors
Dr. Itiel Dror
David Charlton

In an article published in the Journal of Forensic Identification(600/56(4), 2006), Dr. Itiel Dror and David Charlton examined the role that psychological and cognitive factors may play in errors made by latent fingerprint examiners.
The fact that latent fingerprint examiners are human allows for the possibility that errors may result from the way the brain processes information and makes decisions. The authors designed a study to investigate the possibility that inherent psychological and cognitive mechanisms predispose fingerprint and other forensic identification experts to commit such errors.
The authors obtained the cooperation of six fingerprint experts from their pool of volunteers. Each expert had a minimum of five year's experience in examining latent prints as their primary duty. Each was highly trained, certified by a nationally-recognized independent authority, and had successfully completed proficiency testing. None of them had been the subject of a competency review. They were told that their conclusions would be used for an assessment project intended to look at problematic prints and assessments.

A unique set of eight pairs of fingerprints was prepared and tailored for each of the participants. Each set was comprised of fingerprints that the subject had examined in the past. Four pairs of prints had been judged as individualizations and four pairs of prints had been judged as exclusions. Two of each of the pairs were relatively difficult to judge, and two were relatively easy to judge. All of the fingerprints had been obtained from actual crime scenes.

In contrast to a previous study where the participants were told that the prints they were examining were from the Mayfield(Madrid Bombing) case, in this study the authors used a more subtle approach. In two pairs of latent comparisons that that the expert had judged to be exclusions in the past, the participants were told that the suspect had been arrested or had already confessed to the crime. In two pairs of latent comparisons that the expert had judged to be individualizations in the past, the examiners were told that the suspect had been in custody on other charges at the time of the offence. The remaining four of the pairs of latent comparisons were used as controls and no contextual information was provided for them.

When the results were tabulated, it was found that only two out of the six participants remained consistent across the eight experimental trials. Their findings were the same as they had been when they first examined the pairs of fingerprints in the past. The other four changed their findings - one of the experts changed their findings in three cases, while three others changed their findings in one case. In most instances, the changes took place when the participants examined the more difficult latents, and changed their findings from 'individualization' to 'exclusion' or 'cannot decide'. In one case, the examiner changed a previous decision from 'exclusion' to 'individualization'.

The data collected in this study demonstrates that the findings of fingerprint examiners could be vulnerable to contextual information. This vulnerability is most pronounced when dealing with difficult comparisons, but can also be a factor when performing routine comparisons. The fact that two of the six participants did not change any of their findings shows that it is possible to overcome the influence of contextual information.

The authors concluded that more research is needed in a wide range of issues pertaining to individualization, including the aptitude and training of fingerprint examiners; the procedures in place that can filter out contextual bias; and the correct use and integration of technology. The authors believe that the results of such research would reduce the numbers of errors being made.