Evaluating the discriminating power of amino acid ratios on distinguishing dark colored hair samples.

Human hairs are one of the most commonly encountered items of trace evidence. Currently, conventional methods for hair analysis include microscopic comparison and DNA analysis (nuclear and mitochondrial). Each approach has its own drawbacks. Hair proteins are stable and offer an alternative to DNA testing, as demonstrated with proteomics for distinguishing humans. However, proteomics is complicated and requires identifying peptides to remain intact following harsh sample preparation methods. Alternatively, the actual amino acid content of a hair sample may also offer important identifying information and actually requires proteins and peptides to be broken down completely rather than remaining intact. This study evaluated the discriminating power of using hair amino acid ratios to differentiate hair samples from 10 unrelated individuals with dark colored hair. Hair proteins were digested, derivatized, and analyzed using gas chromatography-mass spectrometry. Amino acid ratios were calculated for each individual and comparisons using ANOVA and post-hoc pairwise t-test with Bonferroni correction were made with amino acid ratios for individuals. Overall, out of the 45 possible pairwise comparisons between all hair samples, 38 (84%) were differentiable. Out of the 36 possible pairwise comparisons between brown haired individuals, 32 (89%) were considered differentiable using univariate statistics. Multivariate statistics were also attempted but, overall, univariate models were sufficient for exclusionary purposes. These results indicate that amino acid ratio analysis can potentially be used as an exclusionary method using hair if DNA analysis cannot be performed, or to corroborate conclusions made following microscopic analysis.

Differentiation of Morphologically Similar Human Head Hairs from Two Demographically Similar Individuals Using Amino Acid Ratios.

Human hair is frequently encountered as forensic evidence and can contribute valuable information to investigators. Conventional forensic hair analyses include microscopic hair comparison (MHC) and DNA analysis. However, MHC is not supported by statistics and DNA analysis cannot always be performed. Recent studies have demonstrated that evaluation of differences in the hair proteins may offer an alternate method to these analyses. In this study, an evaluation of the amino acids present in hair was investigated as an approach to differentiate morphologically indistinguishable hair samples from two demographically similar individuals. Proteins in the hair were digested using hydrochloric acid, and the resulting amino acids were derivatized with N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA) for analysis using gas chromatography-mass spectrometry (GC-MS). Eight derivatized amino acids were detected and quantified relative to an internal standard, L-norvaline, and used to construct twenty-eight amino acid ratios. Hair samples were collected from four areas of the head on various days over the course of one month, and no significant differences in amino acid ratios (p-value > 0.05) were observed among the areas of the head, and the ratios were consistent over the time period of this study. Additionally, fifteen of these amino acid ratios were found to be significantly different between the two individuals when compared using a two-sample t-test (p-value ≤ 0.05). These data indicate that amino acid analysis was able to differentiate two morphologically similar hair samples from different individuals and demonstrates the applicability of this method to distinguish similar hair samples when DNA analysis cannot be performed.

False-Positive Enzymatic Alcohol Results in Perimortem Specimens.

Herein, we present 2 cases referred to the North Carolina Office of the Chief Medical Examiner (NC OCME) in which ethanol results reported by different hospital laboratories, using alcohol dehydrogenase (ADH)-based assays, were positive, whereas results of headspace gas chromatography testing performed in the NC OCME laboratory were negative. Literature reports suggest that false-positive ethanol measurements from ADH-based assays can occur when a combination of elevated lactate and lactate dehydrogenase (LD) are present in the specimen. The results were reported in perimortem specimens collected from 2 children with unrelated medical conditions. The cases and associated clinical parameters are considered based on the lactate/LD explanation for the false-positive results, to facilitate the recognition of circumstances that can produce erroneous serum ethanol results.

Methanol Detected in a Subdural Hematoma as an Embalming Artifact.

Analysis of subdural hematomata has been used to suggest antemortem drug concentrations, with the assumption that materials within the hematoma are less subject to metabolism or degradation during any survival period and postmortem interval. We report the case of an 87-year-old woman whose death had not been reported to the coroner's office until postembalming. Autopsy revealed a traumatic brain injury with subdural hematoma causing a mass effect. Testing of the clot indicated a methanol concentration of 51.8 mg%. No additional analyses were detected. These findings suggest that methanol can be present in a postmortem hematoma sample, yet not represent a poisoning. Our findings also suggest that while the interior of hematomata do not necessarily represent completely "protected space" from postmortem diffusion of some blood constituents, such diffusion is not facile, and analysis may still provide useful indications of antemortem drugs present, if not actual concentrations.

Simultaneous quantification of diazepam, flunitrazepam and metabolites in reinforced clostridial medium by liquid chromatography-tandem mass spectrometry.

A novel liquid chromatography-tandem mass spectrometry method was validated for identification and quantification of diazepam, flunitrazepam and metabolites in reinforced clostridial medium (RCM), a complex matrix used to provide the nutrients required for bacterial growth. The method was designed for subsequent use in the investigation of gastrointestinal bacteria as a potential source of postmortem alteration of drugs of abuse and respective metabolite concentrations. A literature review yielded no experimental means or model for the extraction and analysis of samples from RCM or similar bacterial medium. Development and validation of a new experimental method were therefore critical. In future work, this method could be adapted and extended to similar organic compounds of interest. The calibration curves extended from 0.100 to 500 ng/mL. Analyte recoveries ranged from 95 to 119% and matrix effects from 97 to 119%. Bias was ≤±17.6%, within-run precision ≤12.2%, and between-run precision ≤11.7% across all concentration levels. The limits of detection and quantitation ranged from 0.100 to 1 ng/mL. Dilution integrity was maintained for 1:2 and 1:5 dilutions. Analytes were stable through two freeze-thaw cycles and processed samples for 48 h. Method robustness was evaluated by changes in buffer composition and column temperature as well as samples prepared by an alternate analyst.

Production of human metabolites by gastrointestinal bacteria as a potential source of post-mortem alteration of antemortem drug/metabolite concentrations.

Previous studies have demonstrated that bacterial species are capable of transforming complex chemical substances. Several of these species, native to the human gastrointestinal tract, are active in postmortem decomposition. They have potential to cause biotransformations affecting compound-to-metabolite ratios within the human body, especially after death. Investigation of postmortem effects could supply valuable information, especially concerning compound identification and confirmation. The purpose of this research was to investigate the effects of Escherichia coli, Bacteroides fragilis, and Clostridium perfringens on diazepam and flunitrazepam in Reinforced Clostridial Medium, and to compare bacterial biotransformation products to those of human metabolism. A decrease in diazepam concentration between pre- and post-incubation was observed for samples inoculated with Escherichia coli (14.7-20.2%) as well as Bacteroides fragilis (13.9-25.7%); however there was no corresponding increase in concentration for the monitored human metabolites. Flunitrazepam demonstrated a greater concentration loss when incubated with individual bacterial species as well as mixed culture (79.2-100.0%). Samples incubated with Bacteroides fragilis, Clostridium perfringens, and mixed culture resulted in nearly complete conversion of flunitrazepam. Increased 7-aminoflunitrazepam concentrations accounted for the majority of the conversion; however discrepancies in the mass balance of the reaction suggested the possibility of a minor metabolite that was not monitored in the current analysis. These experiments served as a pilot study and proof of concept that can be adapted and applied to a realm of possibilities. Ultimately, this methodology would be ideal to study compounds that are too toxic or lethal for animal and human metabolic investigations.

Evaluation of potential lactate/lactate dehydrogenase interference with an enzymatic alcohol analysis.

The Connecticut Department of Public Safety laboratory recently addressed a legal challenge to a hospital alcohol dehydrogenase (ADH)-based serum ethanol determination based on the suggestion of interference by lactate dehydrogenase (LDH)-catalyzed oxidation of lactate. Both ADH- and LDH-oxidations require NAD(+) (present in excess in the assay). NADH produced by LDH-catalyzed lactate oxidation in the assay is interpreted as derived from ethanol. Hepatic trauma was suggested as the basis for elevated levels of lactate and LDH. Clinical laboratory results were evaluated, specifically serum hepatic enzymes, ions, and anion gap. Aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) were 229 and 144 U/L, respectively (approximately 8x and 4x reference range midpoint values). Na(+), K(+), Cl(-), and CO(2) levels were 143, 3.0, 112, and 20 meq/L, respectively, yielding an anion gap of 8 meq/L (ref. range 8-15). Serum lactate contributes to "unmeasured anions"; hence, the anion gap was inconsistent with a significant lactate elevation. Based on the slight elevation of ASAT and ALAT, LDH levels were estimated to be elevated to no more than 10-fold. Calculation of the amount of LDH and ADH present in the ethanol assay suggest an ADH/LDH ratio of 200:1. Hence, contribution by lactate oxidation to the serum ethanol concentration in this case would have been negligible.

Human identification from the ankle with pre- and postsurgical radiographs.

Fifty-four sets of presurgical ("premortem") and postsurgical ("postmortem") foot and ankle radiographs were retrospectively evaluated to simulate a postmortem identification. The entire foot and ankle was examined in a previous study. The present study evaluates only the ankle for positive identification. Results are consistent with our earlier investigation of pre- and postsurgical foot and ankle radiographic comparisons and indicate that surgical intervention with subsequent healing does not preclude positive identification. However, the ankle contains fewer skeletal features unique to an individual than does the entire foot. Hence, the ankle may be less useful than the foot for establishing positive identification from radiographic comparisons.

Using pre- and post-surgical foot and ankle radiographs for identification.

An evaluation of the effect of surgical intervention on foot and ankle radiographic comparisons was performed. In this study, 34 sets of pre-surgical ("premortem") and post-surgical ("postmortem") foot and ankle radiographs were retrospectively evaluated simulating a postmortem identification. In each radiographic set, the films were separated by a surgical event to reproduce the effects of an alteration in the anatomy. The radiographs included both matches and mismatches. This study also presents a numerical representation of the reliability of a radiographic match following a surgical procedure. Results indicate that surgical intervention with subsequent healing does not preclude positive identification in foot and ankle radiographic comparisons.