Interpretation of glass composition measurements: the effects of match criteria on discrimination capability

The concentrations of ten elements in 209 unrelated glass specimens received as evidence were used to assess the frequencies of errors of false association (Type II errors) using several comparison criteria at specified significance levels (Type I errors). Pairwise comparisons of the samples using either the equal-variance t-test or Welch's modification (unequal variances) result in a small number of errors of false association, even when adjusting the significance level (Bonferroni correction) for multivariate comparisons. At the 95% confidence level (overall Type I error of 0.05, or individual element comparison error of 0.005), only two Type II errors are made in 21736 comparisons (0.009%) when using the equal-variance t-test for comparison of sample means. In this study, the range overlap test using three replicate measurements per specimen results in no errors of false association. Most specimen pairs in this data set are readily discriminated either by differences in the concentrations of several elements or by an extremely large difference in the concentrations of one or more element.     

Development and evaluation of a standard method for the quantitative determination of elements in float glass samples by LA-ICP-MS

Forensic analysis of glass samples was performed in different laboratories within the NITE-CRIME (Natural Isotopes and Trace Elements in Criminalistics and Environmental Forensics) European Network, using a variety of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) systems. The main objective of the interlaboratory tests was to cross-validate the different combinations of laser ablation systems with different ICP-MS instruments. A first study using widely available samples, such as the NIST SRM 610 and NIST SRM 612 reference glasses, led to deviations in the determined concentrations for trace elements amongst the laboratories up to 60%. Extensive discussion among the laboratories and the production of new glass reference standards (FGS 1 and FGS 2) established an improved analytical protocol, which was tested on a well-characterized float glass sample (FG 10-1 from the BKA Wiesbaden collection). Subsequently, interlaboratory tests produced improved results for nearly all elements with a deviation of < 10%, demonstrating that LA-ICP-MS can deliver absolute quantitative measurements on major, minor and trace elements in float glass samples for forensic and other purposes.     

Dual-System Families: Cash Assistance Sequences of Households Involved With Child Welfare

Dual-system families, those involved with the child welfare system and receiving public cash assistance, may be more vulnerable than families connected to only one of the two systems. This study advances our understanding of the heterogeneous and dynamic cash-assistance histories of dual-system families in the post–welfare reform era. With merged administrative data from Washington over the period 1998–2009, we use cluster analysis to group month-to-month sequences of cash-assistance use among households over the 37-month period surrounding child removal. Close to two thirds of families who received any assistance either had a short spell with Temporary Assistance for Needy Families (TANF) or lost TANF. Smaller percentages had steady support. Families who lose assistance are less likely than average to reunify while those who connect to benefits are more likely, suggesting that coordination between systems may serve dual-system families well.     

A multi-site, randomized study of strengths-based case management with substance-abusing parolees

Objectives  

To test whether strengths-based case management provided during an inmate’s transition from incarceration to the community increases participation in community substance abuse treatment, enhances access to needed social services, and improves drug use, crime, and HIV risk outcomes.     

Adherence to Scheduled Sessions in a Randomized Field Trial of Case Management: The Criminal Justice–Drug Abuse Treatment Studies Transitional Case Management Study

The Transitional Case Management (TCM) study, one of the projects of the Criminal Justice Drug Abuse Treatment Studies (CJ-DATS) cooperative, was a multi-site randomized test of whether a strengths-based case management intervention provided during an inmate’s transition from incarceration to the community increases participation in community substance abuse treatment, enhances access to needed social services, and improves drug use and crime outcomes. As in many intervention studies, TCM experienced a relatively large percentage of treatment-group participants who attended few or no scheduled sessions. The paper discusses issues with regard to participation in community case management sessions, examines patterns of session attendance among TCM participants, and analyzes client and case manager characteristics that are associated with number of sessions attended and with patterns of attendance. The average number of sessions (out of 12) attended was 5.7. Few client or case manager characteristics were found to be significantly related to session attendance. Clinical and research implications of the findings and of adherence in case management generally are discussed.     

Characterization and differentiation of aluminum powders used in improvised explosive devices – Part 1: Proof of concept of the utility of particle micromorphometry

Aluminum (Al) powders are commonly used in improvised explosive devices as metallic fuels, a component of explosive mixtures. These powders can be obtained readily from industrial‐scale and consumer products, and produced using unsophisticated “kitchen chemistry” techniques. This research demonstrates the potential of automated particle micromorphometry for comparisons between known source and questioned Al powders recovered from IEDs, as well as for insight into the method of Al powder manufacture. Al powder samples were obtained from legitimate manufacturers, and 56 samples were produced “in‐house” from Al‐containing spray paints and ball‐milled Al foils. Transmitted light microscope images of Al powder particles were acquired using an automated stage with automated z‐focus; 17 size and shape parameters were measured for all particles. Approximately 37,000–2,500,000 particles/sample were analyzed using an open‐source statistical package with customized code. Dimensionality reduction was required for processing the large datasets: eight of the 17 measured variables were selected based on inspection of the correlation matrix. Data from four subsamples from each of the 56 samples produced using “in‐house” methods were analyzed using ANOVA to assess the within‐ and between‐sample variation. High within‐sample variation was noted; however, ANOVA and post‐hoc Tukey's honestly significant difference (HSD) tests demonstrated that the between‐sample variation was substantially larger than the within‐sample variation. Each sample could be differentiated from all other samples in the test set. Future experiments will focus on ways to reduce the within‐sample variation, and additional statistical and microanalytical methods to classify sources and confidently constrain the method of Al powder manufacture.     

The Effects of Building Strong Families: A Healthy Marriage and Relationship Skills Education Program for Unmarried Parents

This article examines the impacts of Building Strong Families, a healthy marriage and relationship skills education program serving unmarried parents who were expecting or had recently had a baby. Based on a random assignment research design, the analysis uses survey data from more than 4,700 couples across eight research sites to estimate program effects. Results varied across sites, with one site having a pattern of positive effects (but no effect on marriage) and another having numerous negative effects. However, when impacts are averaged across all research sites, the findings indicate that the program had no overall effects on couples’ relationship quality or the likelihood that they remained together or got married.     

Score-based likelihood ratios for handwriting evidence

Score-based approaches for computing forensic likelihood ratios are becoming more prevalent in the forensic literature. When two items of evidential value are entangled via a scorefunction, several nuances arise when attempting to model the score behavior under the competing source-level propositions. Specific assumptions must be made in order to appropriately model the numerator and denominator probability distributions. This process is fairly straightforward for the numerator of the score-based likelihood ratio, entailing the generation of a database of scores obtained by pairing items of evidence from the same source. However, this process presents ambiguities for the denominator database generation - in particular, how best to generate a database of scores between two items of different sources. Many alternatives have appeared in the literature, three of which we will consider in detail. They differ in their approach to generating denominator databases, by pairing (1) the item of known source with randomly selected items from a relevant database; (2) the item of unknown source with randomly generated items from a relevant database; or (3) two randomly generated items. When the two items differ in type, perhaps one having higher information content, these three alternatives can produce very different denominator databases. While each of these alternatives has appeared in the literature, the decision of how to generate the denominator database is often made without calling attention to the subjective nature of this process. In this paper, we compare each of the three methods (and the resulting score-based likelihood ratios), which can be thought of as three distinct interpretations of the denominator proposition. Our goal in performing these comparisons is to illustrate the effect that subtle modifications of these propositions can have on inferences drawn from the evidence evaluation procedure. The study was performed using a data set composed of cursive writing samples from over 400 writers. We found that, when provided with the same two items of evidence, the three methods often would lead to differing conclusions (with rates of disagreement ranging from 0.005 to 0.48). Rates of misleading evidence and Tippet plots are both used to characterize the range of behavior for the methods over varying sized questioned documents. The appendix shows that the three score-based likelihood ratios are theoretically very different not only from each other, but also from the likelihood ratio, and as a consequence each display drastically different behavior.     

Forensic significance of bullet lead compositions

The concentrations of seven elements in projectile lead specimens received as evidence were used to assess the frequency of the occurrence of two unrelated samples having indistinguishable compositions. A set of data from 1837 samples was selected for this study from a sampling of 23,054 lead bullets and shot pellets received as evidence in the FBI Laboratory over the period 1989 through 2002. The method used for selection of samples from case submissions ensured that no two samples of the same general type from the same case were included and that no bias was introduced concerning representation of manufacturers or production sources. A total of 1,686,366 pairwise lead sample comparisons were made using the concentrations of the elements Sb, Cu, As, Ag, Bi, Sn, and Cd using a match criterion of two times the sum of the standard deviations of the paired samples. Of the 1837 samples, 1397 samples, or 76%, are distinguishable from every other sample in this study. The total number of indistinguishable sample pairs is 674, for a frequency of 1 out of every 2502 comparisons. The frequency of occurrence of matching samples decreases as the number of measured elements is increased and as the precision of the measurements improves. For bullets in which all seven elements were determined, the match frequency is 1 in 7284. Compositional comparison of bullet lead provides a reliable, highly significant point of evidentiary comparison of potential sources of crime-related bullets.