The Development and Application of Random Match Probabilities to Firearm and Toolmark Identification

The field of firearms and toolmark analysis has encountered deep scrutiny of late, stemming from a handful of voices, primarily in the law and statistical communities. While strong scrutiny is a healthy and necessary part of any scientific endeavor, much of the current criticism leveled at firearm and toolmark analysis is, at best, misinformed and, at worst, punditry. One of the most persistent criticisms stems from the view that as the field lacks quantified random match probability data (or at least a firm statistical model) with which to calculate the probability of a false match, all expert testimony concerning firearm and toolmark identification or source attribution is unreliable and should be ruled inadmissible. However, this critique does not stem from the hard work of actually obtaining data and performing the scientific research required to support or reject current findings in the literature. Although there are sound reasons (described herein) why there is currently no unifying probabilistic model for the comparison of striated and impressed toolmarks as there is in the field of forensic DNA profiling, much statistical research has been, and continues to be, done to aid the criminal justice system. This research has thus far shown that error rate estimates for the field are very low, especially when compared to other forms of judicial error. The first purpose of this paper is to point out the logical fallacies in the arguments of a small group of pundits, who advocate a particular viewpoint but cloak it as fact and research. The second purpose is to give a balanced review of the literature regarding random match probability models and statistical applications that have been carried out in forensic firearm and toolmark analysis.     

The Structure of Citizen Perceptions of Crime and Disorder: New Insights from a Caribbean Community

Objectives

This study builds on existing research from US cities on the construct and discriminant validity of perceptual measures of crime and disorder. It seeks to determine whether citizens distinguish between crime and disorder.

Methods

This study draws on quantitative and qualitative data from a high-crime community in Trinidad and Tobago, a small-island developing nation in the eastern Caribbean. Analysis of the quantitative data relies on exploratory and confirmatory factor analysis methods designed for use with categorical observed variables and continuous latent variables.

Results

In contrast to previous research, we find that citizens do distinguish between physical disorder and general crime, but there is a perceptual overlap for some drug-related offenses and types of social disorder.

Conclusions

This study raises questions about the external validity of research on the relationship between perceptions of crime and disorder conducted in the US, and contributes to ongoing discussions and debates about the meaning of disorder. The findings suggest the need for theory and research to explain how context shapes not only the magnitudes of these perceptions, but also their structures. The results also demonstrate the benefits of mixed-methods research approaches in this area of study.

     

Parents’ knowledge and attitudes about youths’ interrogation rights

Some states and police agencies require youth to consult with parents before or during interrogation by police, yet these policies rely on the untested assumption that parents themselves are knowledgeable about police interrogation practices and youths’ rights. This study assessed knowledge of, and attitudes about, juvenile interrogations in a sample of parents (N?=?294) recruited from urban locales. On average, parents correctly answered fewer than half of the questions about juvenile interrogation practices; knowledge about parental notification procedures was especially poor. At the same time, parents strongly endorsed youths’ rights to support (including support from parents) during police questioning contexts and only moderately endorsed youths’ decision-making autonomy, even for older youth who are legally adults.     

Quality assurance testing of an explosives trace analysis laboratory--further improvements

The Forensic Explosives Laboratory (FEL) operates within the Defence Science and Technology Laboratory (DSTL) which is part of the UK Government Ministry of Defence (MOD). The FEL provides support and advice to the Home Office and UK police forces on matters relating to the criminal misuse of explosives. During 1989 the FEL established a weekly quality assurance testing regime in its explosives trace analysis laboratory. The purpose of the regime is to prevent the accumulation of explosives traces within the laboratory at levels that could, if other precautions failed, result in the contamination of samples and controls. Designated areas within the laboratory are swabbed using cotton wool swabs moistened with ethanol water mixture, in equal amounts. The swabs are then extracted, cleaned up and analyzed using Gas Chromatographs with Thermal Energy Analyzer detectors. This paper follows on from a previous published paper describing the regime and summarizing subsequent results from approximately 6 years of tests. Lessons learned and improvements made over the period are also discussed. Monitoring samples taken from surfaces within the trace laboratories and trace vehicle examination bay have, with few exceptions, revealed only low levels of contamination, predominantly of RDX. Analysis of the control swabs, processed alongside the monitoring swabs, has demonstrated that in this environment the risk of forensic sample contamination, assuming all the relevant anti-contamination procedures have been followed, is so small that it is considered to be negligible. The monitoring regime has also been valuable in assessing the process of continuous improvement, allowing sources of contamination transfer into the trace areas to be identified and eliminated.     

Examining the Overlap and Prediction of Multiple Forms of Child Maltreatment,Stressors, and Socioeconomic Status: A Longitudinal Analysis of Youth Outcomes

Analyses were conducted to examine the extent of overlap and predictive strength of multiple forms of child maltreatment and stressors internal and external to the family. Findings suggest a strong association between child maltreatment (physical and sexual abuse, neglect, and exposure to domestic violence) and stressors (family conflict, personal problems of parents, and external constraints on the family). After controlling for stressors, family socioeconomic status, and child gender, a general construct of child maltreatment was predictive of internalizing and externalizing behaviors in adolescents. Specific effects of child physical and sexual abuse were revealed in these longitudinal structural equation model tests.

Risk factors for violence and relational aggression in adolescence

Analyses examined risk factors for seventh-and ninth-grade youth categorized as nonoffenders, physically violent, relationally aggressive, and both violent and relationally aggressive. Bivariate and multivariate results showed that relationally aggressive youth were elevated on most risks above levels for nonoffenders but lower than those for youth who were violent alone or violent in combination with relational aggression. Youth who were both relationally aggressive and violent did not differ from those who were violent alone on most risk factors examined. Peer, individual, and family risks were among the strongest predictors.     

Characteristics and Prediction of Cranial Crush Injuries in Children*†

Abstract: This study documents four clinical cases of fatal crush injuries to children between 1.5 and 6 years of age with correlations between modeled stress and clinically observed fracture patterns. The clinical case fractures were concentrated in the basicranium, bridged the impact sites, and traversed the middle cranial fossa in the area of the spheno‐occipital synchondrosis. The crushing forces from these cases were recreated on a simplified finite element model of a cranium by applying bilateral pressures to corresponding regions. Numerous trials were run to develop a representative pattern of principal stress directions. In all cases, the highest tensile stresses were located on the basicranium and corresponded to the observed fracture path(s). These results suggest that prefailure stress field diagrams may predict fracture propagation paths, although these will not be exact. Also, these analyses indicate that quasi‐static bilateral loading of the cranium may lead to predictable fracture of the basicranium.     

Cloud forecasting: Legal visibility issues in saturated environments

The advent of cloud computing has brought the computing power of corporate data processing and storage centers to lightweight devices. Software-as-a-service cloud subscribers enjoy the convenience of personal devices along with the power and capability of a service. Using logical as opposed to physical partitions across cloud servers, providers supply flexible and scalable resources. Furthermore, the possibility for multitenant accounts promises considerable freedom when establishing access controls for cloud content. For forensic analysts conducting data acquisition, cloud resources present unique challenges. Inherent properties such as dynamic content, multiple sources, and nonlocal content make it difficult for a standard to be developed for evidence gathering in satisfaction of United States federal evidentiary standards in criminal litigation. Development of such standards, while essential for reliable production of evidence at trial, may not be entirely possible given the guarantees to privacy granted by the Fourth Amendment and the Electronic Communications Privacy Act. Privacy of information on a cloud is complicated because the data is stored on resources owned by a third-party provider, accessible by users of an account group, and monitored according to a service level agreement. This research constructs a balancing test for competing considerations of a forensic investigator acquiring information from a cloud.     

Assessing a Child’s Experience of Multiple Maltreatment Types: Some Unfinished Business

Available research indicates that maltreated children frequently experience multiple types of maltreatment, although relatively few studies examine this issue directly. Review of existing studies also shows that, when investigated, maltreatment types are often correlated. However, from study to study the strength of associations among maltreatment types varies considerably, apparently due to methodological differences, such as differences in operational definitions of the maltreatment types, composition of samples and/or method of scaling used. Failure to account for overlap among maltreatment types can result in a misleading picture of a child’s trauma history. This in turn can lead to an inaccurate evaluation of the relationship between a child’s victimization experiences and later developmental outcomes. The wide variation in correlations among the maltreatment types from study to study raises questions about the validity of the different operational definitions used. Improving the construct validity of the maltreatment type measures is proposed as the means to obtaining more consistent results. Steps by which to achieve this objective are outlined. This project (1 RO1 HD049767-01A2) is co-funded by the National Institute of Child Health and Human Development (NICHD) and the Office of Behavioral and Social Sciences Research (OBSSR). The authors wish to thank M. Jean Russo for reviewing a draft of this paper.