Spectral enhancement of leucocrystal violet treated footwear impression evidence in blood

The results presented demonstrate the capacity for spectral enhancement to substantially improve the forensic examination of footwear impressions in blood treated with leucocrystal violet (LCV). The UV-Vis absorption spectra were generated of (i) an aqueous solution of leucocrystal violet, (ii) leucocrystal violet in 3% H(2)O(2), (iii) LCV working solution and (iv) whole blood added to LCV working solution. The resultant fluorescence emission spectra were subsequently generated (lambda(ex)=630nm, lambda(em)=661-900nm). The results indicate that the UV-Vis absorption spectra of an unbuffered solution of whole blood with LCV working solution produces a strong absorbance curve with a maxima at 630nm. Subsequent excitation at this wavelength and generation of the emission spectrum in the fluorescence mode indicates that a solution of whole blood added to LCV working solution is an extremely weak fluorophore. Therefore, to enable an adequate and timely enhancement of blood impression evidence treated with LCV utilising either visible fluorescence or infrared luminescence requires (i) selection of the most appropriate excitation wavelength (lambda(ex)) and emission wavelength (lambda(em)) with extremely narrow band pass filters, which in the absence of substrate matrix interference is excitation at 630nm producing the emission maxima at 665nm and (ii) a visual enhancement system such as a CCD colour IR video camera with image integration.     

Confidence and accuracy of eyewitness identification from lineups

Recent studies of confidence-accuracy correlations in eyewitness-identification experiments have produced highly variable results (Deffenbacher, 1980; Wells & Murray, 1984) with some correlations near 0 (Malpass & Devine, 1981) and others as high as 0.5 (Brigham et al., 1982). Much of this variability may be accounted for by differences, in the design of the research. Specifically, lineup experiments in which the to-be-identified person (target) is always present tend to produce higher confidence-accuracy correlations than studies also providing blank or target-absent lineups replacing the target with a lookalike. A reanalysis of previously collected data (Lindsay & Wells, 1980; Wallbridge & Lindsay, 1982) revealed that lineup foils (nontargets) were identified with significantly less confidence than targets or lookalikes but that targets and lookalikes were identified with equal confidence. Two experiments were conducted to test the hypothesis that confidence of identification is a function of the similarity of the identified person to the original target. The first experiment using nonstudent subjects (n=53) and multiple targets (n=14) to increase generalizability, demonstrated that the person in the lineup who most closely resembled the target was identified with the highest mean level of confidence. The second experiment examined confidence in identification following a crime staged for 260 introductory psychology students. The results indicated that the similarity of foils to the target (established by independent ratings) was predictive of both the frequency and confidence of identification of faces.     

Witnessing-Condition Heterogeneity and Witnesses' Versus Investigators' Confidence in the Accuracy of Witnesses' Identification Decisions

Undergraduate participants were tested in 144 pairs, with one member of each pair randomly assigned to a witness role and the other to an :investigator role. Each witness viewed a target person on video under good or poor witnessing conditions and was then interviewed by an investigator, who administered a photo lineup and rated his or her confidence in the witness. Witnesses also (separately) rated their own confidence. Investigators discriminated between accurate and inaccurate witnesses, but did so less well than witnesses' own confidence ratings and were biased toward accepting witnesses' decisions. Moreover, investigators' confidence made no unique contribution to the prediction of witnesses' accuracy. Witnesses' confidence and accuracy were affected in the same direction by witnessing conditions, and there was a substantial confidence–accuracy correlation when data were collapsed across witnessing conditions. Confidence can be strongly indicative of accuracy when witnessing conditions vary widely, and witnesses' confidence may be a better indicator than investigators'     

Adapting to Prison Life: A Qualitative Examination of the Coping Process among Incarcerated Offenders

Research on general strain theory has demonstrated the impact of strain on decisions to engage in crime and delinquency. However, people differ in their responses to strain and only some resort to crime or delinquency. There remain gaps in our knowledge of when, and under what conditions, individuals will react to strain with offending behavior. We rely on interviews with 40 incarcerated men to understand how they cope with specific prison strains, and why they make such coping choices. We find considerable variation in inmates’ coping responses. They use a variety of coping strategies—behavioral, cognitive, and emotional—and only some of these strategies involve offending. Our findings indicate that responses to prison strain are partly a function of past experience with strains, including prior experimentation with coping techniques. Results highlight the unfolding nature of the coping process and expose factors that deserve further attention in tests of GST.     

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.     

A DNA-based approach for the forensic identification of Asiatic black bear (Ursus thibetanus) in a traditional Asian medicine

Attempts to prevent illegal trade in bile and gallbladders from Asiatic black bears, Ursus thibetanus, are hampered by difficulties associated with identifying such items. We extracted DNA from bile crystals of unknown species origin and generated partial cytochrome b (cyt b) sequences using either universal primers (positioned in conserved regions of cyt b), or primers designed on existing U. thibetanus sequences (UT). Species origin was determined by aligning resolved sequences to reference sequence data. The universal primers were unsuitable for U. thibetanus identification when multiple species templates were present in the samples. The UT primers amplified U. thibetanus DNA from all sample extracts, including those containing mixed species templates. The amplified fragment can distinguish U. thibetanus from the most closely related species, U. americanus, a distinct advantage of DNA sequencing over the methods currently used to analyze suspected U. thibetanus bile.