Validation of a new method of providing case-specific time-of-death estimates using cadaver temperatures

The near ubiquitous presence of numerical simulation has made case-specific calculations of body temperatures following death possible so that accurate calculations of body temperatures can provide valuable information for estimating the time of death and can aid in forensic investigations. Here, a computational approach is described that has been validated against multiple, independent, and experimental investigations. The approach only requires one subjective input parameter (the heat transfer coefficient). A simple algorithm serves as a guidepost to the selection of this parameter. The algorithm incorporates clothing and the space in which the body is housed. Heat transfer coefficients that range from h = 2 W/m²/°C for bodies that are heavily clothed to h = 9 W/m²/°C for bodies that are nude (in air). The method also requires setting of ambient temperature conditions (ambient temperature)—however, that input is often available. The paucity of inputs makes this technique remarkably easy to employ. The new method is also able to calculate cadaver cooling rates for situations where the cadaver is in a timewise or spatially changing thermal environment (diurnal temperature variations, bodies partially submerged in water, changes to weather, insolation, etc.). Results from the present calculations are compared with a large body of measurements from the literature; it was found that the predictions and measurements were in excellent agreement, regardless of the ambient temperature conditions and the nature of the clothing of the body. This new calculation approach can be used with reasonable accuracy for determining cadaver cooling and time since death.     

Examination of acetone findings in suspected drug-facilitated sexual assaults: A case series

Acetone presence in human biological specimens can result from exogenous administration or endogenous production, resulting from diabetes, dietary composition, alcoholism, and stress response. Victims of drug-facilitated sexual assaults (DFSA) are understood to experience enhanced stress. At the Harris County Institute of Forensic Sciences (HCIFS), DFSA drug testing includes analysis of volatile compounds, ethanol, methanol, isopropanol, and acetone, by headspace gas chromatography/flame ionization detection. The prevalence of acetone-positive specimens in DFSA casework has been observed to exceed that of other human performance case types. In this report, DFSA cases received between 2019 and 2021 (n = 393) were reviewed and 41 acetone-positive cases were detailed. Overall, nearly 11% of the DFSA cases had acetone-positive blood or urine specimens, where 3% identified acetone only, 6% identified acetone and other drug(s), and 2% identified acetone, ethanol, and other drug(s). Acetone concentrations ranged from 0.010 to 0.147 g/100 mL in urine. Other drugs such as nor-carboxy-Δ⁹-tetrahydrocannabinol, amphetamine, methamphetamine, ethanol, and benzoylecgonine were commonly detected. Elevated stress response encountered during DFSAs may facilitate the mechanism behind enhanced acetone production leading to increased identification. Limited availability of victim medical history precludes understanding the contribution of other disease states or physiological conditions. Nonetheless, the identification of acetone in DFSA specimens supports its potential as a biomarker of trauma in forensic toxicology casework and warrants future research within the community.     

On the challenge of unambiguous identification of fentanyl analogs: Exploring measurement diversity using standard reference mass spectral libraries

Fentanyl analogs are a class of designer drugs that are particularly challenging to unambiguously identify due to the mass spectral and retention time similarities of unique compounds. In this paper, we use agglomerative hierarchical clustering to explore the measurement diversity of fentanyl analogs and better understand the challenge of unambiguous identifications using analytical techniques traditionally available to drug chemists. We consider four measurements in particular: gas chromatography retention indices, electron ionization mass spectra, electrospray ionization tandem mass spectra, and direct analysis in real time mass spectra. Our analysis demonstrates how simultaneously considering data from multiple measurement techniques increases the observable measurement diversity of fentanyl analogs, which can reduce identification ambiguity. This paper further supports the use of multiple analytical techniques to identify fentanyl analogs (among other substances), as is recommended by the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG).     

The effectiveness of various strategies to improve DNA analysis of formaldehyde-damaged tissues from embalmed cadavers for human identification purposes

Formalin-fixed tissues provide the medical and forensic communities with alternative and often last resort sources of DNA for identification or diagnostic purposes. The DNA in these samples can be highly degraded and chemically damaged, making downstream genotyping using short tandem repeats (STRs) challenging. Therefore, the use of alternative genetic markers, methods that pre-amplify the low amount of good quality DNA present, or methods that repair the damaged DNA template may provide more probative genetic information. This study investigated whether whole genome amplification (WGA) and DNA repair could improve STR typing of formaldehyde-damaged (FD) tissues from embalmed cadavers. Additionally, comparative genotyping success using bi-allelic markers, including INDELs and SNPs, was explored. Calculated random match probabilities (RMPs) using traditional STRs, INDEL markers, and two next generation sequencing (NGS) panels were compared across all samples. Overall, results showed that neither WGA nor DNA repair substantially improved STR success rates from formalin-fixed tissue samples. However, when DNA from FD samples was genotyped using INDEL and SNP-based panels, the RMP of each sample was markedly lower than the RMPs calculated from partial STR profiles. Therefore, the results of this study suggest that rather than attempting to improve the quantity and quality of severely damaged and degraded DNA prior to STR typing, a more productive approach may be to target smaller amplicons to provide more discriminatory DNA identifications. Furthermore, an NGS panel with less loci may yield better results when examining FD samples, due to more optimized chemistries that result in greater allelic balance and amplicon coverage.     

Toward maintaining canine training aid integrity: Visualizing contamination and testing storage materials for a non-hazardous canine training aid

Contamination of canine training aids is a pervasive issue that may lead to incorrect canine discrimination of target odors. It is therefore important to properly store training materials to maintain their integrity and efficiency. First, this study demonstrated the potential for contamination using GloGerm™ as a proxy for odor/particulate transfer. Then, eight types of containers were evaluated to determine (1) the ability to prevent odor permeation and (2) the likelihood of maintaining the ab/adsorbed odor. Lastly, a longitudinal study evaluated how the permeation of the target odor changed over time. Analysis occurred using a direct analysis in real-time mass spectrometer (DART-MS) to detect triacetone triperoxide (TATP) from the non-hazardous canine training aid known as the polymer odor capture-and-release (POCR) system. Results showed that Mylar and Opsak bags were most effective for short-term storage, maintaining low levels of ab/adsorption. Over time, the amount of TATP permeating through the primary containers and collecting in a secondary container (i.e., outer packaging) increased at 1 week and decreased thereafter (up to 4 months). The amount of TATP collecting in the primary containers, however, increased up to 1 month and decreased thereafter.     

Rapid detection of synthetic cannabinoid receptor agonists impregnated into paper by attenuated total reflectance Fourier transform infrared spectroscopy

The last few years have witnessed the change in the modalities of smuggling of synthetic cannabinoid receptor agonists (SCRAs) by impregnating them in mail envelopes and fast parcels. Considering the aforementioned scenario, it is important to develop a portable technique to identifying SCRAs through packages. The purpose of this research was to detect SCRAs impregnated into substrates of paper using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Three SCRAs that included 5F-PB-22, AB-FUBINACA and AKB-48 were purchased from Sigma Aldrich. The three SCRAs and four cutting agents were impregnated into paper of variable thickness at four concentrations (10, 15, 20, and 25 mg/mL). Spectra were collected over the wavenumber range of 650–4000 cm⁻¹ using ATR-FTIR spectroscopy and were exported to Matlab 2020b where data analysis was applied. The FTIR spectral data was able to show the three SCRAs could be detected on paper using ATR-FTIR spectroscopy and quantitatively modeled using the partial least squares regression algorithm. Principal component analysis showed separate clustering for the compounds that crystallized (5F-PB-22, AB-FUBINACA and caffeine) onto the papers surface from those impregnated into the bulk of the paper (AKB-48 and procaine) with the latter situated near blank papers in score plots. In summary, ATR-FTIR spectroscopy has proven to be a successful non-destructive technique in detecting and quantifying a selection of SCRAs impregnated into paper.     

Collecting touch DNA from glass surfaces using different sampling solutions and volumes: Immediate and storage effects on genetic STR analysis

Touch DNA has become increasingly important evidence in todays' forensic casework. However, due to its invisible nature and typically minute amounts of DNA, the collection of biological material from touched objects remains a particular challenge that underscores the importance of the best collection methods for maximum recovery efficiency. So far, swabs moistened with water are often utilized in forensic crime scene investigations for touch DNA sampling, even though an aqueous solution provokes osmosis, endangering the cell's integrity. The aim of the research presented here was to systematically determine whether DNA recovery from touched glass items can be significantly increased by varying swabbing solutions and volumes compared with water-moistened swabs and dry swabbing. A second objective was to investigate the possible effects of storage of swab solutions prior to genetic analysis on DNA yield and profile quality when stored for 3 and 12 months, as is often the case with crime scene samples. Overall, the results indicate that adapting volumes of the sampling solutions had no significant effect on DNA yield, while the detergent-based solutions performed better than water and dry removal, with the SDS reagent yielding statistically significant results. Further, stored samples showed an increase in degradation indices for all solutions tested, but no deterioration in DNA content and profile quality, allowing for unrestricted processing of touch DNA samples stored for at least 12 months. One further finding was a strong intraindividual change in DNA amounts observed over the 23 deposition days which may be related to the donor's menstrual cycle.     

Alternative direct-to-amplification cell lysis techniques for forensically relevant non-sperm cells

While efforts have been made to reduce the pervasive backlog of sexual assault evidence collection kits, the actual laboratory process remains very time-consuming due to the requirement of a differential lysis step before DNA purification, as well as intricate mixture analysis towards the end of the DNA workflow. Recently, an alternative, direct-to-amplification sperm lysis method (using 1 M NaOH) was identified. However, a direct cell lysis method for non-sperm cells has not been identified yet. Thus, the primary objective of this work was to find an alternative method that is quick, inexpensive, and does not require multiple purification steps for the lysis of non-sperm cells in sexual assault samples. In this study, vaginal swab samples were lysed with the control method, prepGEM™, as well as six alternative reagents: alkaline buffer with 25–200 mM NaOH, high-salt stain extraction buffer, modified radioimmunoprecipitation assay (RIPA) buffer, mammalian protein extraction reagent (M-PER™), digitonin buffer, and urea/thiourea buffer. Quantification using Quantifiler® Trio of vaginal and semen lysates revealed that the alkaline (25 mM NaOH) and M-PER™ methods were efficient for the lysis of vaginal epithelial cells without substantial sperm cell lysis. Following quantification, analysis of STR profiles from vaginal lysates revealed that the M-PER™ method showed promising results across all metrics examined, including the percentage of detected STR alleles, mean peak heights, peak height ratio, and interlocus balance. Thus, this method was recommended as an alternative to the traditional differential lysis method for non-sperm cells given its ability to produce amplification-ready lysates without any DNA purification step.     

Classical stimulants in Dallas County: A retrospective review of toxicological,seized drug,and demographical data from 2017 to 2022

Cocaine and methamphetamine remain highly abused drugs in the United States due to their euphoric effects. This study examines classical stimulant casework, defined as cases positive for methamphetamine and/or cocaine, received by the Toxicology Laboratory and the Drug Analysis Laboratory at the Dallas County Southwestern Institute of Forensic Sciences from local law enforcement agencies and/or the Office of the Medical Examiner (OME) between January 1, 2017, and December 31, 2022. Methamphetamine positivity increased from 10.4% to 20.3% in the Toxicology Laboratory over the 6 years, whereas cocaine positivity remained relatively stable at approximately 17%. Similarly, in the Drug Analysis Laboratory, the methamphetamine positivity rate changed from 24.8% to 33.2%, whereas cocaine identification remained stable at approximately 20%. Blood concentrations of methamphetamine in OME cases ranged from 10.1–42,740.0 ng/mL while they were lower in DWI casework ranging from 10.2–2385.0 ng/mL. The blood concentration trends of cocaine were similar to methamphetamine, with OME casework ranging higher (10.0–24,501.0 ng/mL) than DWI casework (10.2–371.6 ng/mL). Polydrug use was evident for both methamphetamine and cocaine in postmortem cases, and the top three most frequently co-occurring drug/drug class were opioids/opiates, cannabinoids, and ethanol. The results from this study aid in the understanding of historical usage trends of cocaine and methamphetamine in Dallas County and how those trends have changed over time as newer stimulant drugs have emerged.