Serious Youth Gun Offenders and the Epidemic of Youth Violence in Boston

Boston, like many other major cities, experienced a sudden increase in youth homicides during the late 1980s and early 1990s. Research evidence suggests that the recent epidemic of urban youth violence was intensely concentrated among criminally active young black males residing in disadvantaged urban neighborhoods rather than all young black males residing in disadvantaged black neighborhoods. Other researchers, however, suggest that there was a diffusion of guns and gun violence from youth involved in street crack markets to youth outside the drug trade who armed themselves primarily for self-protection against the armed criminally active youth. In this paper, criminal history data are analyzed to determine whether the criminal profile of Boston arrested youth gun offenders changed over time and micro-level data on youth gun assault incidents in Boston are examined to unravel whether there were noteworthy changes in the nature of these violent events over time. The results of these analyses suggest that the youth violence epidemic in Boston was highly concentrated among serious youth gun offenders rather than a diffusion of guns away from the street drug trade, gangs, and criminally active youth.     

Limitations of ZAF correction factors in the determination of calcium/phosphorus ratios: important forensic science considerations relevant to the analysis of bone fragments using scanning electron microscopy and energy-dispersive x-ray microanalysis

A series of calcium phosphate standards having calcium/phosphorus (Ca/P) molar ratios of 0.50, 1.00, 1.50, and 1.67, respectively, was prepared for bulk specimen analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDXA). The standards were mounted on carbon planchettes as either pure crystals or crystals embedded in epoxy resin. Ten different samples of each embedded and non-embedded standard were analyzed in a JEOL 100 CX electron microscope interfaced with a Kevex 8000 EDXA system using a lithium-drifted silicon detector and a multichannel analyzer. The Ca/P ratios were determined by calculating both net peak intensities without matrix corrections and atomic kappa-ratios using the MAGIC V computer program with ZAF correction factors for quantitative analysis. There was such extensive absorption of phosphorus X-rays in standards embedded in an epoxy matrix that the observed Ca/P ratios were statistically compatible with four different standards ranging in theoretical Ca/P ratios from 1.0 to 1.67. Although the non-embedded crystals showed a greater separation in the Ca/P ratios, both methods of preparation produced serious flaws in analysis. Direct application of the discovery of this caveat to the identification of suspected bone fragments for forensic science purposes is discussed.