Evaluating Bioinformatic Pipeline Performance for Forensic Microbiome Analysis*,†,‡

Microbial communities have potential evidential utility for forensic applications. However, bioinformatic analysis of high-throughput sequencing data varies widely among laboratories. These differences can potentially affect microbial community composition and downstream analyses. To illustrate the importance of standardizing methodology, we compared analyses of postmortem microbiome samples using several bioinformatic pipelines, varying minimum library size or minimum number of sequences per sample, and sample size. Using the same input sequence data, we found that three open-source bioinformatic pipelines, MG-RAST, mothur, and QIIME2, had significant differences in relative abundance, alpha-diversity, and beta-diversity, despite the same input data. Increasing minimum library size and sample size increased the number of low-abundant and infrequent taxa detected. Our results show that bioinformatic pipeline and parameter choice affect results in important ways. Given the growing potential application of forensic microbiology to the criminal justice system, continued research on standardizing computational methodology will be important for downstream applications.     

A Comparison of Coronary Artery Stenosis Estimates Made by Forensic Pathologists and Medical Students

Previous studies suggest cardiovascular pathologists are less accurate than noncardiovascular pathologists (e.g., clinical pathologists) in estimating the degree of coronary artery stenosis. To further investigate the effect of training on accurate estimation of coronary artery stenosis, we designed a study to compare the accuracy of estimates made by forensic pathologists versus medical students. Six forensic pathologists and twelve medical students each independently examined 24 images of coronary artery cross sections and gave an estimate of the degree of stenosis. When comparing all 24 images, the forensic pathologists had a median difference between the estimated percentage of stenosis and actual percentage of stenosis of −12.380 and the medical students had a median difference of −16.50 (p-value of 0.08542). In estimating the percentage of stenosis, training in forensic pathology does not guarantee significantly improved accuracy compared with medical students. Our study showed no consistent statistically significant difference between estimates given by forensic pathologists and by medical students.     

Recommendations for Maintaining a Dermestid Beetle Colony (Dermestes maculatus) for Processing Human Remains

Dermestid beetles (Dermestes maculatus De Geer 1774) are small carrion insects characterized by a rounded or oval-shaped body and white abdomen with black markings. Given their natural propensity to consume soft tissue throughout various stages of decomposition, biological anthropologists have sought to use dermestids as a forensic processing method in addition to traditional chemical tissue removal techniques. Although useful, most of the existing academic literature regarding the upkeep of dermestid colonies for skeletal remains processing either lack specificity or are outdated. Additionally, nonacademic sources that contain information regarding dermestid maintenance are often disjointed, resulting in a difficulty to replicate habitat construction and ideal environmental conditions. Therefore, this technical note presents recommendations for anthropologists interested in establishing and maintaining a D. maculatus population. These recommendations are based on our experiences using several dermestid colonies to process five unembalmed human heads, procured from an anatomical gift company for a larger study on gunshot trauma. Aspects of the dermestids’ environment that are crucial for the management of a healthy colony include the type of bedding, food, water, and containment method used, in addition to maintaining appropriate temperature ranges (24–27°C) and humidity levels (35–73%). Although habitat construction and dermestid maintenance involve materials that are relatively inexpensive and readily available, setting up and maintaining a D. maculatus colony can be laborious and time consuming and should only be undertaken when the volume of casework is such that this investment would be offset.     

Development of a Novel Finger-Trigger Interface for Trigger Pull Measurement

Trigger pull is the force that needs to be exerted on the trigger to discharge a firearm. The measurement of trigger pull can assist in the evaluation of the safety, function, and manufacturing characteristics associated with a firearm during the forensic firearm examination process. Nonetheless, the accuracy and uncertainty of trigger pull measurements may be affected by the measuring device, test procedure, and environmental conditions. In this work, an innovative finger-trigger interface device was developed to facilitate accurate trigger pull measurements. The idea was to reduce the variation related to the position of the measurement device on the trigger in existing measuring methods and devices. Three force sensors based on different technologies were initially evaluated. While two of the three sensors failed to produce data, the miniature capacitive plate sensor exhibited high precision and a linear response over the range of typical trigger pulls. To examine the effects of the finger-trigger interface on trigger pull measurement, different sensor housing prototypes were designed in silico and 3D printed for the construction of three finger-trigger interface devices. The performance of each finger-trigger interface device was evaluated by measuring the trigger pulls of several selected firearms and comparing the data to a previously published study. Our preliminary results demonstrated the novel finger-trigger interface device offered a new way to measure trigger pull in situ with acceptable accuracy and precision.     

Organizational and Human Factors Affecting Forensic Decision-Making: Workplace Stress and Feedback

Although forensic examiners operate in a stressful environment, there is a lack of understanding about workplace stress and feedback. These organizational and human factors can potentially impact forensic science judgments. In this study, 150 practicing forensic examiners from one laboratory were surveyed about their experiences of workplace stress, and the explicit and implicit feedback they receive. Forensic examiners reported that their high stress levels originated more from workplace-related factors (management and/or supervision, backlogs, and the pressure to do many cases) than from personal related factors (family, medical, and/or financial). The findings showed that a few (8%) of the forensic examiners sometimes felt strong implicit feedback about what conclusions were expected from them and that some (14%) also strongly felt that they were more appreciated when they helped to solve a case (e.g., by reaching a “match” as opposed to an “inconclusive” conclusion). Differences were found when comparing workplace stress and feedback levels across three core forensic science fields (forensic biology, chemistry, and latent prints) and across career stages (early, mid, and late). Gaining insights into the stress factors within a workplace and explicit and implicit feedback has implications for developing policies to improve the well-being, motivation, and performance of forensic examiners.     

Postmortem Computed Tomography in Firearm Homicides: A Retrospective Case Series,

Postmortem computed tomography (PMCT) is integrated into the evaluation of decedents in several American medical examiner offices and medicolegal death investigative centers in many other countries. We retrospectively investigated the value of PMCT in a series of firearm homicide cases from a statewide centralized medical examiner’s office that occurred during 2016. Autopsies were performed or supervised by board-certified forensic pathologists who reviewed the PMCT scans prior to autopsy. PMCT scans were re-evaluated by a forensic radiologist blinded to the autopsy findings and scored by body region (head–neck, thoracoabdominal, and extremities). Injury discrepancies were scored using a modified Goldman classification and analyzed with McNemar’s test. We included 60 males and 20 females (median age 31 years, range 3–73). Based on PMCT, 56 (79.1%) cases had injuries relevant to the cause of death in a single body region (24 head–neck region, 32 thoracoabdominal region). Out of these 56 cases, 9 had a missed major diagnosis by PMCT outside that region, including 6 extremity injuries visible during standard external examination. Yet all had evident lethal firearm injury. We showed that PMCT identifies major firearm injuries in homicide victims and excludes injuries related to the cause of death in other regions when a single body region is injured. Although PMCT has a known limited sensitivity for soft tissue and vascular pathology, it can be combined with external examination to potentially reduce or focus dissections in some of these cases depending on the circumstances and medicolegal needs.     

The Error in “Error Rate”: Why Error Rates Are So Needed,Yet So Elusive

Establishing error rates is crucial for knowing how well one is performing, determining whether improvement is needed, measuring whether interventions are effective, as well as for providing transparency. However, the flurry of activities in establishing error rates for the forensic sciences has largely overlooked some fundamental issues that make error rates a problematic construct and limit the ability to obtain a meaningful error rate. These include knowing the ground truth, establishing appropriate databases, determining what counts as an error, characterizing what is an acceptable error rate, ecological validity, and transparency within the adversarial legal system. Without addressing these practical and theoretical challenges, the very notion of a meaningful error rate is limited.     

How do body-worn cameras affect the amount and makeup of police-initiated activities? A randomized controlled trial in Milwaukee,Wisconsin

Journal of Experimental Criminology - Examine how the amount and makeup of police-initiated activities changed after the introduction of body-worn cameras (BWCs). From May 21 to November 22, 2016,...