Assessing the strengths and limitations of quantitative micromorphometry for the forensic examination of small arms propellant towards brand identification.

Smalls arms propellants (SAP) also known as canister powders are readily accessible and cost-effective materials that firearms enthusiasts can acquire for the legitimate assembly of ammunition. These attributes also make SAPs advantageous for the construction of improvised explosive devices (IEDs). Thus, there is a need to develop robust metrics for the characterization of propellants to provide investigative leads as well as for comparisons between known and recovered residues. The goal of this research was to investigate the utility of a high-throughput, non-destructive, and low-cost quantitative automated image analysis routine for the characterization and discrimination of SAP. For this project, 204 one-pound canisters of smokeless propellant (powder) were acquired from local and online sources. These samples represent nine manufacturers and 154 unique brands. From this set, five brands were selected to assess the intra- and inter-lot variability. Eight parameters, which encompass size- and shape-dependent metrics were measured for each sample. A total of ∼85,000 granules (∼680,000 measurements) were analyzed using linear discriminant analysis. A detailed assessment of the variables shows that the size-dependent metrics provide the greatest amount of sample discrimination. Overall accuracy of the method to correctly classify a test subset of data to the brand level is ∼84.72%. The results from this study provide a framework in which to interpret smokeless propellant micromorphometry in the context of intelligence purposes for initial stages of criminal investigations, and for traditional comparisons between known and unknown samples.

Death by paint thinner.

A 38-year-old Caucasian male, reportedly missing for four days, was found dead 40 feet down a steep ravine, apparently after jumping down the cliff. Two rectangular cans of paint thinner, 1-qt and 1-gal sizes, were found in his vehicle at the top of the cliff. The autopsy report indicated that the decedent was normal except for the heart and myocardium, the lung parenchyma, and the gastric and esophageal mucosa. The stomach contents revealed a brownish liquid with a nearly clear, thick, oily film, and the small and large bowels showed oily liquid with a strong odor of a petroleum distillate. Toxicological analysis was negative for ethanol and common drugs of abuse. Valproic acid, diphenhydramine, and norsertraline where found in therapeutic concentrations, and sertraline, diazepam, and nordiazepam were found in subtherapeutic levels. Bupropion metabolites were also detected. Static adsorption-elution, commonly used in fire debris analysis, was used to examine the brain, liver, lung, blood, and urine. A liquid-liquid extraction was performed on the vitreous humor. The stomach contents and samples from the paint thinner cans were diluted with carbon disulfide. All but the blood and vitreous contained a medium petroleum distillate. The stomach content was consistent with the liquid from the one-gallon can. Chromatograms suggest differential metabolism and/or distribution among the different organs.