Finding the way forward for forensic science in the US:a commentary on the PCAST report

A recent report by the US President’s Council of Advisors on Science and Technology (PCAST) [1] has made a number of recommendations for the future development of forensic science. Whereas we all agree that there is much need for change, we find that the PCAST report recommendations are founded on serious misunderstandings. We explain the traditional forensic paradigms of match and identification and the more recent foundation of the logical approach to evidence evaluation. This forms the groundwork for exposing many sources of confusion in the PCAST report. We explain how the notion of treating the scientist as a black box and the assignment of evidential weight through error rates is overly restrictive and misconceived. Our own view sees inferential logic, the development of calibrated knowledge and understanding of scientists as the core of the advance of the profession

Theoretical value of the recommended expanded European Standard Set of STR loci for the identification of human remains

We have undertaken a series of simulations to assess the effectiveness of commercially available sets of STR loci, including the loci recommended for inclusion in the expanded European Standard Set, for the purpose of human identification. A total of 9200 genotype simulations were performed using DNA · VIEW. The software was used to calculate likelihood ratios (LRs) for 23 groups of relatives, and to determine the probability of identification given scenarios that ranged between 10 and 250,000 victims. The additional loci included in the recommended expanded European Standard Set, when used in conjunction with the Identifiler® kit, significantly improved the typical LRs for tested scenarios and the likely success of providing correct identifications

Development of European standards for evaluative reporting in forensic science : The gap between intentions and perceptions

Criminal justice authorities of EU countries currently engage in dialogue and action to build a common area of justice and to help increase the mutual trust in judicial systems across Europe. This includes, for example, the strengthening of procedural safeguards for citizens in criminal proceedings by promoting principles such as equality of arms. Improving the smooth functioning of judicial processes is also pursued by works of expert working groups in the field of forensic science, such as the working parties under the auspices of the European Network of Forensic Science Institutes (ENFSI). This network aims to share knowledge, exchange experiences and come to mutual agreements in matters concerning forensic science practice, among them the interpretation of results of forensic examinations. For example, through its Monopoly Programmes (financially supported by the European Commission), ENFSI has funded a series of projects that come under the general theme ‘Strengthening the Evaluation of Forensic Results across Europe’. Although these initiatives reflect a strong commitment to mutual understanding on general principles of forensic interpretation, the development of standards for evaluation and reporting, including roadmaps for implementation within the ENFSI community, are fraught with conceptual and practical hurdles. In particular, experience through consultations with forensic science practitioners shows that there is a considerable gap between the intentions of a harmonised view on principles of forensic interpretation and the way in which works towards such common understanding are perceived in the community. In this paper, we will review and discuss several recurrently raised concerns. We acknowledge practical constraints such as limited resources for training and education, but we shall also argue that addressing topics in forensic interpretation now is of vital importance because forensic science continues to be challenged by proactive participants in the legal process that tend to become more demanding and less forgiving

When evaluating DNA evidence within a likelihood ratio framework, should the propositions be exhaustive?

We seek to develop a rational approach to forming propositions when little information is available from the outset, as this often happens in casework. If propositions used when evaluating evidence are not exhaustive (in the context of the case), then there is a theoretical risk that an LR greater than one may be associated with a proposition in the numerator that - if all meaningful propositions had been considered - would in fact have a lower posterior probability after consideration of the evidence. Ideally, all propositions should be considered. However, with multiple propositions, some terms will be larger than others and for simplification very small terms can be neglected without changing the order of magnitude of the value of the evidence (i.e. LR). Our analysis shows that mathematically a contributor's DNA can be assumed to be present under both prosecution and alternative propositions (H <sub>p</sub> and H <sub>a</sub> ) if there is a reasonable prior probability of their DNA being present and their inclusion is supported by the profile. This is because the terms associated to these sub-propositions will dominate our LR. For example, in the absence of specific information, when considering two persons of interest (POI) as potential contributors to a mixed DNA profile we suggest the assumption of one when examining the presence of the other, after checking that both collectively explain the profile well. This represents more meaningful propositions and allows better discrimination. Slooten and Caliebe have shown that the overall LR is the weighted average of LRs with the same number of contributors (NoC) under both propositions. The weights involve both an assessment of the probability of the crime scene DNA profile and the probability of this NoC given the background information

Further comment on "Low copy number typing has yet to achieve "general acceptance"" by Budowle, B., et al, 2009. Forensic Sci. Int. Genetics: Supplement Series 2, 551-552

This paper provides further comment on “Low copy number typing has yet to achieve “general acceptance” ” by Budowle, B., et al, 2009. Forensic Sci. Int. Genetics: Supplement Series 2, 551–552 http://dx.doi.org/10.1016/j.fsigss.2009.08.08