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.     

Once a sex offender … always a sex offender: Myth or fact?

In the current focus upon prisons, prisoners, and correctional treatment, there also seems to be an increase in fear of sex offenders. “Once a sex offender, always a sex offender” has become a common belief. The following study, however, has concluded that this phrase is mistaken and misleading. The actual number of sex offenders who recidivate are few. This study, and many prior to this one, have concluded that upwards of 65% donot commit another sex offense. Most reoffenses are committed between 1 and 5 years after release, and the percentage of reoffenders declines rapidly after. A positive correlation was found between length of time spent in prison and recidivism rates. Further studies are suggested to follow up this interesting finding. Authors' Note: This paper was originally presented at the Society for Police and Criminal Psychology meeting in Austin Texas, October, 2001. The authors wish to thank Amy Phenix, Mary Moss, Roxanne Lieb, Elizabeth Drake, Lee Keene, Neal Christopherson, and Larry Greenfeld.     

The regular article tracking developments at the national level in key European countries in the area of IT and communications – co-ordinated by Herbert Smith LLP and contributed to by firms across Europe

This column provides a concise alerting service of important national developments in key European countries. Part of its purpose is to compliment the journal's feature articles and briefing notes by keeping readers abreast of what is currently happening “on the ground” at a national level in implementing EU level legislation and international conventions and treaties. Where an item of European National News is of particular significance, CLSR may also cover it in more detail in the current or a subsequent edition.