The Critical Role of Statistics in Demostrating the Reliability of Expert Evidence

Federal Rule of Evidence 702, which covers testimony by expert witnesses, allows a witness to testify “in the form of an opinion or otherwise” if “the testimony is based on sufficient facts or data” and “is the product of reliable principles and methods” that have been “reliably applied.” The determination of “sufficient” (facts or data) and whether the “reliable principles and methods” relate to the scientific question at hand involve more discrimination than the current Rule 702 may suggest. Using examples from latent fingerprint matching and trace evidence (bullet lead and glass), I offer some criteria that scientists often consider in assessing the “trustworthiness” of evidence to enable courts to better distinguish between “trustworthy” and “questionable” evidence. The codification of such criteria may ultimately strengthen the current Rule 702 so courts can better distinguish between demonstrably scientific sufficiency and “opinion” based on inadequate (or inappurtenant) methods

Realizing Reliability in Forensic Science from the Ground Up

This Article emphasizes that forensic flaws persist and that deficiencies in forensic science have harrowing implications for criminal justice. In the wake of numerous calls for forensic reform, I propose that we use existing models and frameworks already in place to improve the quality and cost of the U.S. forensic science program, rather than creating an entirely new and unaffordable system. At bottom, this Article calls for collaboration between crime labs, universities and research centers, and the criminal justice system with the goal of making forensic science more reliable

Method for estimating potential recognition capacity of texture-based biometrics

When adopting an image-based biometric system, an important factor for consideration is its potential recognition capacity, since it not only defines the potential number of individuals likely to be identifiable, but also serves as a useful figure-of-merit for performance. Based on block transform coding commonly used for image compression, this study presents a method to enable coarse estimation of potential recognition capacity for texture-based biometrics. Essentially, each image block is treated as a constituent biometric component, and image texture contained in each block is binary coded to represent the corresponding texture class. The statistical variability among the binary values assigned to corresponding blocks is then exploited for estimation of potential recognition capacity. In particular, methodologies are proposed to determine appropriate image partition based on separation between texture classes and informativeness of an image block based on statistical randomness. By applying the proposed method to a commercial fingerprint system and a bespoke hand vein system, the potential recognition capacity is estimated to around 10^36 for a fingerprint area of 25  mm^2 which is in good agreement with the estimates reported, and around 10^15 for a hand vein area of 2268  mm^2 which has not been reported before

The Proficiency of Experts

Expert evidence plays a crucial role in civil and criminal litigation. Changes in the rules concerning expert admissibility, following the Supreme Court\u27s Daubert ruling, strengthened judicial review of the reliability and the validity of an expert\u27s methods. Judges and scholars, however, have neglected the threshold question for expert evidence: whether a person should be qualified as an expert in the first place. Judges traditionally focus on credentials or experience when qualifying experts without regard to whether those criteria are good proxies for true expertise. We argue that credentials and experience are often poor proxies for proficiency. Qualification of an expert presumes that the witness can perform in a particular domain with a proficiency that non-experts cannot achieve, yet many experts cannot provide empirical evidence that they do in fact perform at high levels of proficiency. To demonstrate the importance ofproficiency data, we collect and analyze two decades of proficiency testing of latent fingerprint examiners. In this important domain, we found surprisingly high rates of false positive identifications for the period 1995 to 2016. These data would qualify the claims of many fingerprint examiners regarding their near infallibility, but unfortunately, judges do not seek out such information. We survey the federal and state case law and show how judges typically accept expert credentials as a proxy for proficiency in lieu of direct proof of proficiency. Indeed, judges often reject parties\u27 attempts to obtain and introduce at trial empirical data on an expert\u27s actual proficiency. We argue that any expert who purports to give falsifiable opinions can be subjected to proficiency testing and that proficiency testing is the only objective means of assessing the accuracy and reliability ofexperts who rely on subjective judgments to formulate their opinions (so-called black-box experts ). Judges should use proficiency data to make expert qualification decisions when the data is available, should demand proof of proficiency before qualifying black-box experts, and should admit at trial proficiency data for any qualified expert. We seek to revitalize the standard for qualifying experts: expertise should equal proficiency

Assignment of the evidential value of a fingermark general pattern using a Bayesian network

Abstract: When visible on a fingermark, the general pattern maintains its importance in the fingerprint examination procedure, since the difference between the general pattern of a fingermark and a fingerprint is sufficient for exclusion. In the current work, the importance of the general pattern is extended by evaluating the strength of evidence of a match given corresponding general pattern. In current practice (due to the lack of statistical support for the general pattern evidence) the fingerprint examiners assign personal probabilities to the general pattern evidence based on their knowledge and experience, while in this work the probabilities are calculated using a Bayesian Network which is fed by empirical data. 1

Analyzing the viability of direct PCR for use in conjunction with cyanoacrylate enhanced fingerprints

Efficient methods for DNA analysis are desperately needed in laboratories due to the influx in DNA analysis requests. The current DNA processing methods are costly, time consuming, and involve multiple tube changes, increasing the risk of contamination. However, the use of direct PCR can simplify the DNA analysis process by eliminating the extraction, purification and quantitation steps. Presently, the FBI Quality Assurance Standard 9.4 requires all evidence samples to be quantitated. As a result, the direct PCR method of DNA processing cannot be implemented on evidence samples at this time. Direct PCR presents the opportunity to provide efficient DNA analysis, making the investigation of this process an important endeavor for the forensic community. This study sought to evaluate the ability of direct PCR to generate DNA profiles from fingerprints that have been previously enhanced using cyanoacrylate. Traditional methods of DNA analysis used on fingerprints post chemical processing have resulted in full DNA profiles. In addition, direct PCR has been successful on a wide variety of samples containing potential inhibitors, even those visualized with various dactyloscopic powders. No studies have assessed the ability of using direct PCR to acquire DNA profiles from cyanoacrylate treated fingerprints, representing a gap in knowledge for the forensic community. An area of concern for the use of direct PCR is the loss of purification steps meant to remove PCR inhibitors, which could be problematic for analysis of chemically processed fingerprints. Therefore, the assessment of the viability of direct PCR on these types of evidence samples is of critical importance. Participants deposited fingerprints onto glass slides that were subsequently treated with cyanoacrylate. 60 samples were processed using direct PCR and 60 samples were processed through a traditional extraction method. Results were evaluated based on percent recoverability, calculated based on the number of alleles observed over the number of alleles expected. Traditional methods were shown to have the greatest success overall with 53% of samples having at least one correct allele call, however direct PCR showed some success with only 23%. These results indicate that processing cyanoacrylate fumed fingerprint samples using direct PCR is possible and further experimentation and optimization could potentially increase these success rates

On the importance of rare features in AFIS-ranked latent fingerprint matched templates

Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Krish, R.P. ; Fierrez, J. ; Ramos, D. ; Wang, R.; "On the importance of rare features in AFIS-ranked latent fingerprint matched templates" in 47th International Carnahan Conference on Security Technology, Medellin, 2013, pp. 1-6Proceedings of 47th International Carnahan Conference on Security Technology, Medellin, October 2013In this paper, we introduce an algorithm to generate a score from the matched templates derived by the forensic examiner at the ACE-V stage. Such a score can be viewed quantitatively as a measure of confidence of the forensic examiner for the given latent and impression prints. This quantitative measure can be used in statistics-based evidence evaluation frameworks. Together with the description and evaluation of new realistic forensic casework driven score computation, we also exploit this experimental framework to show the importance of type attributes for minutiae in terms of its discriminating ability in forensic scenarios. We derive the conclusion that together with reliably extracted typical minutiae features, the presence of rare minutiae features helps to improve the measure of confidence of the forensic examiner at the ACE-V stage.R.K. and R.W. are supported by Marie Curie Fellowships under project BBfor2 (FP7-ITN-238803). This work has also been partially supported by Spanish Guardia Civil, Cátedra UAM-Telefónica, and projects Bio-Shield (TEC2012-34881) and Contexts (S2009/TIC-1485)