Using spectral information in forensic imaging

Improved detection of forensic evidence by combining narrow band photographic images taken at a range of wavelengths is dependent on the substance of interest having a significantly different spectrum from the underlying substrate. While some natural substances such as blood have distinctive spectral features which are readily distinguished from common colorants, this is not true for visualization agents commonly used in forensic science. We now show that it is possible to select reagents with narrow spectral features that lead to increased visibility using digital cameras and computer image enhancement programs even if their coloration is much less intense to the unaided eye than traditional reagents. The concept is illustrated by visualising latent fingermarks on paper with the zinc complex of Ruhemann's Purple, cyanoacrylate-fumed fingerprints with Eu(tta)(3)(phen), and soil prints with 2,6-bis(benzimidazol-2-yl)-4-[4'-(dimethylamino)phenyl]pyridine [BBIDMAPP]. In each case background correction is performed at one or two wavelengths bracketing the narrow absorption or emission band of these compounds. However, compounds with sharp spectral features would also lead to improved detection using more advanced algorithms such as principal component analysis.     

The Good and Bad of Social Change: Ambivalence Toward Activist Groups

Inherent to any substantive social change is the disruption of the status quo. To the extent that individuals are motivated to preserve the current social system (e.g., Jost & Banaji, British Journal of Social Psychology, 33, 1–27, 1994), even social change in pursuit of positive goals might evoke ambivalent reactions. Although activist groups might elicit positivity because they are assumed to have positive qualities and they seek positive goals, they might evoke negativity because their actions disrupt the current social system. These experiments examined two different forms of disruption of the status quo. In Experiment 1, a group gaining power elicited greater ambivalence than a group losing power, regardless of the valence of the group’s goal. Importantly, the conditions that evoked ambivalence did not inhibit behavioral support. Experiment 2 found that a new group elicited more ambivalence than an established group when pursuing a positive goal. Consistent with theories emphasizing maintenance of the status quo, these findings demonstrate that attitudes toward activist groups do not derive solely from self-interest.