Journal of forensic sciences最新文献

The illegal drug market is constantly evolving, with new drugs being created and existing ones being modified. Adulterants are often added to the mix, and the primary substance may be secretly replaced by a new one. Once-known tablets can now be vastly different from what they are sold as, all due to the pursuit of profit and evasion of current drug regulations. These alterations in drug composition pose a threat to society, as their effects are still not well understood. Therefore, it is crucial for police intelligence and public health development to obtain the chemical profiles of illicit drugs. This study presents the chemical fingerprinting of ecstasy tablets seized in the state of Rio de Janeiro (Brazil) between 2012 and 2021. The tablet samples were weighed, extracted, diluted with methanol, and acidified before analysis using gas chromatography high-resolution mass spectrometry and attenuated total reflection Fourier transform infrared spectroscopy. The major constituents found were MDMA and clobenzorex, with fewer occurrences of MDA, MDEA, and 2C-B. The results also indicate that the occurrence of mega-events in the study location impacted the chemical fingerprints of ecstasy. A total of 27 combinations of cutting agents, including caffeine, ephedrine, and anesthetics, were identified. Samples composed of clobenzorex were observed throughout the evaluated period in areas near highways, suggesting that this product is mainly used by truck drivers. These findings can help police intelligence units anticipate the behavior of the illicit market during major events, identify traffic routes, and support public health initiatives.

In forensic entomology, determining the age of a larva from a body to estimate time since death is commonly performed through the measurement of a physical trait. Gene expression has been studied as an alternative age estimation approach, but the storage conditions required for these studies are different than those used in forensic entomological casework. Studies analyzing gene expression prioritize the preservation of RNA, which requires fresh tissue and ultra-cold storage. Casework, in contrast, utilizes hot water killing specimens that may not be analyzed for a long period after collection. In the current study, the impact of hot water killing on gene expression was assessed for larval samples of the forensically important blow fly, Cochliomyia macellaria. Successful amplification of the sex-determining gene, transformer, was tested across larvae ranging in size from 3.22 to 16.85 mm in length after storage times of 1–2 weeks, 4–5 weeks, and 8–9 weeks at 4°C in RNAlater. Larvae hot water killed were processed in tandem with larvae stored live to allow for a direct assessment of the impact of boiling on gene expression. As expected, the transformer gene was successfully amplified in all larvae stored live. For the hot water-killed larvae, the success rate was only slightly lower, with 3 out of 75 larvae not generating a sex-specific band pattern. The results show gene expression can be used for hot water-killed samples, though future work across different genes, species, and extending to quantitative gene expression methods is needed.

Several studies have recently attempted to estimate practitioner accuracy when comparing fired ammunition. But whether this research has included sufficiently challenging comparisons dependent upon expertise for accurate conclusions regarding source remains largely unexplored in the literature. Control groups of lay people comprise one means of vetting this question, of assessing whether comparison samples were at least challenging enough to distinguish between experts and novices. This article therefore utilizes such a group, specifically 82 attorneys, as a post hoc control and juxtaposes their performance on a comparison set of cartridge case images from one commonly cited study (Duez et al. in J Forensic Sci. 2018;63:1069–1084) with that of the original participant pool of professionals. Despite lacking the kind of formalized training and experience common to the latter, our lay participants displayed an ability, generally, to distinguish between cartridge cases fired by the same versus different guns in the 327 comparisons they performed. And while their accuracy rates lagged substantially behind those of the original participant pool of professionals on same-source comparisons, their performance on different-source comparisons was essentially indistinguishable from that of trained examiners. This indicates that although the study we vetted may provide useful information about professional accuracy when performing same-source comparisons, it has little to offer in terms of measuring examiners' ability to distinguish between cartridge cases fired by different guns. If similar issues pervade other accuracy studies, then there is little reason to rely on the false-positive rates they have generated.

Several code-based methods have been created for comparing the frontal sinus in skeletal identification scenarios. However, little is known regarding matched-pair accuracy rates of these methods or how varying image modalities may affect these rates. The goals of this study were to validate the exclusion rates and to establish matched-pair accuracy rates of two well-cited coding methods, Cameriere et al. [23] and Tatlisumak et al. [24]. Additionally, individual variables were assessed for consistency in scoring between image modalities. Using a sample of U.S. African American, Native American, and European American females and males (n = 225), we examined individual variable scoring and string codes between two different image modalities (radiographs and CT-based 3D models). Arcades showed poor scoring consistency between modalities (p < 0.001). Although exclusion rates were similar to those reported in the original studies (93%–96%), matched-pair accuracy rates were low (13%–18%). None of the demographics (collection, sex, age, ancestry, and orientation) had an effect on the odds of a match. Interobserver and intraobserver analyses showed moderate to near-perfect agreement for all variables except supraorbital cells, which had minimal to no agreement. Currently, we do not recommend the application of these frontal sinus coding methods independent of other supporting identification methods given low variable consistency and accuracy rates. Visual identification should still be used to include or exclude an identification when using the frontal sinus.

The crystal violet (CV) staining technique represents a prevalent approach for the development of latent fingerprints, especially on adhesive tape surfaces. Nevertheless, the technique necessitates intricate formulations to augment its performance. In this investigation, an optimized CV staining protocol was developed, characterized by the absence of residual dye on the target substrates and the capability of facilitating fingerprint visualization under ambient light conditions. Four donors, comprising two males and two females, deposited natural fingerprints on various substrates, including glass microscope slides, aluminum foil, and 115 g glossy coated paper, without any specific guidelines. Fingerprints developed using cyanoacrylate fuming served as benchmarks and were contrasted with those generated through alternative methods: CV, ardrox, rhodamine 6G, powdering, and the optimized CV staining protocol. The fingerprint development experiment was replicated at seven distinct time intervals, encompassing 1 day, 1 week, 1, 3, 6, 9, and 12 months, resulting in a dataset of 420 fingerprints. The evaluation of fingerprint identifiability employed a scoring system established by the Home Office Centre for Applied Science and Technology. The results indicated that the optimized CV staining technique demonstrated superior performance, boasting a 92.9% rate of identifiable fingerprint development in contrast to other employed methodologies. Consequently, this optimized CV staining approach is recommended as an efficient, rapid, and straightforward critical dyeing method, applicable to a wide array of substrates in forensic investigations.

This Letter is a response to “Uncertainty in probabilistic genotyping of low template DNA: A case study comparing STRmix™ and TrueAllele®,” a Journal of Forensic Sciences (JFS) Case Report published online in February 2023 [1].

In a California criminal case, a man was accused of drug possession. At the defendant's request, two drug packages were tested for DNA using short tandem repeat (STR) markers. Both items were two-person mixtures that gave similar match statistic results.

On one item, Cybergenetics TrueAllele® probabilistic genotyping (PG) software found a strong exclusionary match statistic for the defendant of one over 1.2 million, with a false-negative error rate of one over 222 million. On the same item, ESR's STRmix™ PG program produced a weaker exclusionary match statistic of one over 24.

There was no trial. Based on the exculpatory DNA evidence, the prosecutor dropped the more serious DNA-related possession charge and offered a plea agreement. The court accepted the defendant's plea in March 2023.

The TrueAllele and STRmix PG software programs qualitatively agreed. Their likelihood ratio (LR) match statistics both supported the hypothesis that the defendant did not contribute his DNA to the drug package evidence. However, the magnitude of the LR match statistics differed between the software programs.

This letter briefly explains why the two PG software results differed. As JFS requested, we address some issues raised in the Case Report [1]. A more extensive response [2] to the paper [1] was posted online in May 2023, discussing 20 topics and examining 120 assertions.

The two programs were given different amounts of STR input data. TrueAllele is a fully Bayesian system capable of looking at all the (allelic and non-allelic) peak data without relying on laboratory-imposed data thresholds. Most other PG software applies peak height thresholds to limit the amount of input data. Peak heights are measured in relative fluorescent units (rfu).

TrueAllele used 210 data peaks across all 21 GlobalFiler™ STR loci, or 10 peaks per locus. At a 40 rfu threshold, the STRmix program saw 24 peaks across 14 loci, or just 1.7 peaks per locus. This 1.7 peak density is insufficient for an informative analysis of a two-person mixture, since at least three or four peaks would be needed. The 88% reduction in STRmix data peaks, relative to TrueAllele input, accounts for the observed LR output differences.

We tested STRmix on the STR data at different thresholds, ranging from 0 rfu to 90 rfu, in 10 rfu increments. The weakest STRmix subsource LR value in our sensitivity study was 1 over 3.35 (using 11 peaks at a high 90 rfu threshold), while the strongest LR was 1 over 30.5 million (38 peaks at a low 20 rfu threshold). Less STRmix input data gave less output identification information; more data yielded more information.

At

Editor,

The article I published in February 2023 discussed a case in which two probabilistic genotyping (PG) programs were used to analyze the same DNA mixture using the same data file [1]. The mixture was found on a plastic bag containing illegal drugs. Whether the defendant was a contributor to this DNA mixture became an issue in the case.

Answering this question posed a technical challenge because there were at least two contributors and the total quantity of DNA in the mixture was only 92 pg. The major contributor was female, which ruled out the male defendant, so the key question is whether the defendant could have been a minor contributor. The amount of DNA from the minor contributor (or contributors) was very low. An analysis of peak heights suggested at least a 4:1 ratio between the major and minor contributor(s). The quantity of male DNA in the mixture was estimated to be only 6.9 pg.

Two different PG programs, STRmix™ and TrueAllele® (TA), were used to compare the defendant's DNA profile to the mixture. Both programs produced exculpatory findings supporting the hypothesis that the defendant was not a contributor, although the strength of support differed dramatically: TA produced likelihood ratios (LRs) as high as 16.7 million, whereas STRMix produced LRs ranging from 24 to 5 [1]. My article discussed differences between the programs that might explain the different LRs and questioned whether any such findings are sufficiently trustworthy and reliable to be used in court. It also questioned the way these findings were reported.

Individuals associated with both STRMix [2] and TA [3] have now responded to my article. They presented new data that helped explain why the LRs produced by the programs were so different. The difference arose largely from the use of different analytic thresholds: TA took account of many low-level (<40 rfu) peaks that were ignored by STRMix. I commend both groups for doing empirical studies to help explain why the two programs produced such different findings.

It is still unclear, however, which of the reported findings is more trustworthy, or indeed whether either should be trusted. While it is now clear that the LRs produced by STRMix were less extreme because the analyst applied an analytic threshold, those who responded to my article appear to disagree about whether such a threshold is necessary or helpful. The group led by John Buckleton, one of the creators of STRMix, expressed concern about reliance on low-level peaks: “Most of us are wary of very low peak heights. This feeling of discomfort is developed from a large body of experience noting the pernicious effects of artifacts that pass the analysis stage” [2]. Whether a lower threshold increases or decreases accuracy can only be determined, they argue, by testing the accuracy of the PG program across a range of ATs with known samples of the type in questi

This pilot study examines whether the Young Adult Habitual Offender Program (YAHOP), an intensive and outpatient program, is related to a reduction in the general risk of recidivism, common forensic symptomology as well as cognitive distortions. The program integrity (PI) was assessed, with the intent to explore the relationship between the level of PI and any changes in several outcome variables. Additionally, the study examines whether participants with a migration background benefitted equally from YAHOP compared to participants with a native Dutch background. The sample comprised n = 90 high-risk young adult offenders. Results show a decrease in general risk of recidivism. The dynamic risk factors delinquent social network, insufficient impulse control, and dysfunctional problem-solving skills also show a decrease, as well as the forensic symptoms of aggression and anger. Effect sizes are small, except for anger, which has a medium effect size. We found no change in cognitive distortions and problematic substance use. YAHOP shows to be responsive and culturally sensitive, as the participants with a migration background show a significant decrease in general risk of recidivism. No moderator analysis was conducted due to an overall low level of program integrity. After improving program integrity, full-scale quantitative research is needed as YAHOP has the potential as a promising desistance program for high-risk offenders, as in this study the 56 non-completers were also included.

The purpose of this study was to examine factors affecting video analysts' decisions in marking the vertex of the head and foot point and corresponding inter-observer marking variances when conducting height analysis on individuals seen in video. Nineteen video analysts participated in an exercise at the 2022 Ontario Forensic Video Analysts' Association (OFVAA) conference where they were asked to mark the vertex of the head and a corresponding foot point of a “suspect” on extracted video frames in a variety of positions and with different headwear (no headwear, baseball cap, and hoodie). A height scale with discrete marking points located at the same positions as where the suspect was positioned was also included in a separate image set, offering a comparison to the suspect. Marked points for all analysts were overlayed onto the respective image frame for visual observations. Summary statistics were used for data interpretation. This study demonstrated that factors such as the suspect's proximity to the camera and suspect's headwear affected the variability and range of marking, which has a direct correlation to the estimated height of the suspect. In general, when the region to be marked was larger, the variability was also larger. This study also demonstrates that marking errors were significantly reduced when discrete marking locations were present such as on a height scale. The average percentage difference of height was most notable, approximately 3%, when the suspect was wearing a hoodie and was at a position closest to the camera. The range of the percentage difference was also the highest at this position, which was 10.6%. In comparison, the height scale had a maximum percent height difference of 0.6% at position D-5, the furthest position from the camera. The range at this location was approximately 2%, which was also the highest range value for the height scale. Future studies should consider suspect posture and look at how these errors may be minimized by examining the best locations to mark the head and foot points under different scenarios.