This project aims to develop a statistical measure of the uncertainty of the decisions made on the friction ridge evidence (i.e., evidential value of fingerprint comparison), which ultimately can be referred to as a scientific basis of the identification decisions made in friction ridge analysis.
Friction ridge analysis in crime scene investigation is one of the crucial forensic methods to find the suspects and victims of crime and solve cases. Latent fingerprints—the friction ridge patterns from fingertips left at crime scenes and photographed or lifted from the surfaces—are commonly examined by following a methodology called Analysis, Comparison, Evaluation, and Verification (ACE-V). The ACE-V methodology involves latent examiners to (i) assess the value of latent fingerprints, (ii) mark features in the latent images, and (iii) make identification decisions on the pairs of latent and its potential mates retrieved from reference databases. The critical decisions made by the latent examiners include:
Although friction ridge patterns as forensic evidence are highly admissible in courts of law, the lack of scientific basis of the ACE-V procedure has brought concerns due to subjectivity in latent examiner's decisions (an examiner's decision can be affected by the level of expertise, bias after exposure to additional information of the case, workload that hampers his focus and attention to detail, etc.)  and inconsistency (an examiner's decisions made on the same pair of fingerprints at different time points may not be identical; or multiple examiners' decisions on a single pair of prints may not be unanimous) . The 2009 National Academy of Science report pointed out the increased need for scientific research in the evaluation of methods used in forensic science, such as bias quantification, validation, and estimates of accuracy and precision in different contexts. In view of the Daubert ruling , forensic evidence is being subjected to rigorous standards, including empirical testing, known or potential error rate, and standards controlling the analysis procedure.
A need for the scientific underpinning of friction ridge analysis in forensics has been greatly emphasized in order to achieve the robustness and transparency in procedure and decision making in latent fingerprint examination. Towards this goal, this project aims to develop a statistical measure of the uncertainty of the decisions made on the friction ridge evidence (i.e., evidential value of fingerprint comparison), which ultimately can be referred to as a scientific basis of the identification decisions made in friction ridge analysis.
For a pair of latent and fingerprint from suspect, the evidential value of fingerprint comparison is comprised of three components:
In other words, we would like to answer the following question: Given a pair of latent print and its potential mate from the suspect, what is the probability that (i) we observe this evidence in favor of individualization decision, (ii) we observe this evidence in favor of exclusion decision, and (iii) the evidence does not lead to either of individualization or exclusion decisions, but to inconclusive decision.
The ratio of 1) to 2) is known as likelihood ratio which is widely used in DNA analysis and has been recently introduced to friction ridge analysis by Champod and Neumann [6, 7].
In order to establish the three components of the evidential value of fingerprint comparisons, we will conduct the research in two phases, namely population study and evidential value assessment of latent comparisons.
Phase I: Population Study
- Intra-class variability due to skin distortion
- Inter-class variability, in particular, close non-mated fingerprints that two impostor fingers share partial ridge structure.
We will update our results on the following databases.
 SWGFAST defines suitability or sufficiency as the determination that there is adequate quality and quantity of detail in an impression for further analysis, comparison or to reach a conclusion .