Characterization and differentiation of aluminum powders used in improvised explosive devices – Part 1: Proof of concept of the utility of particle micromorphometry

Aluminum (Al) powders are commonly used in improvised explosive devices as metallic fuels, a component of explosive mixtures. These powders can be obtained readily from industrial‐scale and consumer products, and produced using unsophisticated “kitchen chemistry” techniques. This research demonstrates the potential of automated particle micromorphometry for comparisons between known source and questioned Al powders recovered from IEDs, as well as for insight into the method of Al powder manufacture. Al powder samples were obtained from legitimate manufacturers, and 56 samples were produced “in‐house” from Al‐containing spray paints and ball‐milled Al foils. Transmitted light microscope images of Al powder particles were acquired using an automated stage with automated z‐focus; 17 size and shape parameters were measured for all particles. Approximately 37,000–2,500,000 particles/sample were analyzed using an open‐source statistical package with customized code. Dimensionality reduction was required for processing the large datasets: eight of the 17 measured variables were selected based on inspection of the correlation matrix. Data from four subsamples from each of the 56 samples produced using “in‐house” methods were analyzed using ANOVA to assess the within‐ and between‐sample variation. High within‐sample variation was noted; however, ANOVA and post‐hoc Tukey's honestly significant difference (HSD) tests demonstrated that the between‐sample variation was substantially larger than the within‐sample variation. Each sample could be differentiated from all other samples in the test set. Future experiments will focus on ways to reduce the within‐sample variation, and additional statistical and microanalytical methods to classify sources and confidently constrain the method of Al powder manufacture.     

When crimes are joined at trial

In two experiments, subject-jurors read evidence from actual criminal cases, decided on the guilt of the defendant, and answered several additional questions. The defendant was accused of one charge (murder or rape) or two charges (both murder and rape). In both experiments, the defendant was more likely to be convicted of either crime if the two charges were joined in one trial. Trait ratings indicated that the defendant was perceived in a more negative way when standing trial on two offenses. The order in which the charges were heard had no effect, nor did instructions to subjects to judge the cases separately.Portions of this paper were presented at the American Psychology-Law Society Meeting in Cambridge, Massachusetts, October, 1981. The research was supported by a grant from NSF to Elizabeth Loftus.     

Effects of Necessary,Sufficient, and Indirect Causation on Judgments of Criminal Liability

Law and Human Behavior - When has one essentially committed a crime? When are one's actions necessary for its occurrence or sufficient to bring it about under normal circumstances? Participants...     

Construing Motive in Videotaped Killings: The Role of Jurors' Attitudes Toward the Death Penalty

Death-qualified jurors are generally able to impose the death penalty, whereas excludable jurors are generally either unable or unwilling to do so. A long line of research studies has shown that the former are more likely than the latter to convict criminal defendants. Ellsworth (1993) argues that jurors' attitudes toward the death penalty predict verdicts because they are embedded in a cluster of beliefs and theories about the criminal justice system. Her studies show that jurors interpret ambiguous conduct based on these belief structures. The present study examines the possibility that death penalty attitudes also influence jurors' conceptions of criminal intent. We showed mock jurors the filmed murder of a convenience store clerk and examined the inferences they drew from this evidence. Jurors who favored the death penalty tended to read criminal intent into the defendant's actions and jurors who opposed the death penalty were less likely to do so. These data provide further explanation of the conviction-proneness of death-qualified jurors.