Zapata Félix, López-López María, Amigo José Manuel, García-Ruiz Carmen
Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering and University Institute of Research in Police Sciences (IUICP), University of Alcalá, Ctra. Madrid-Barcelona km 33.6, 28871 Alcalá de Henares (Madrid), Spain.
Department of Fundamental Chemistry, Federal University of Pernambuco, Av. Prof. Moraes Rego, 1235 - Cidade Universitária, Recife, Brazil; Department of Food Science, University of Copenhagen, Rolighedsvej 30 - Frederiksberg C, Copenhagen, Denmark.
Forensic Sci Int. 2018 Jan;282:80-85. doi: 10.1016/j.forsciint.2017.11.025. Epub 2017 Nov 22.
Multispectral images of clothing targets shot at seven different distances (from 10 to 220cm) were recorded at 18 specific wavelengths in the 400-1000nm range to visualize the gunshot residue (GSR) pattern. Principal component analysis (PCA) showed that the use of violet-blue wavelengths (430, 450 and 470nm) provided the largest contrast between the GSR particles and the white cotton fabric. Then, the correlation between the amount of GSR particles on clothing targets and the shooting distance was studied. By selecting the blue frame of multispectral images (i.e. the blue frame in the red-green-blue (RGB) system which falls at 470nm), the amount of pixels containing GSR particles was accounted based on the intensity of pixels in that frame. Results demonstrated that the number of pixels containing GSR exponentially decreases with the shooting distance from 30 to 220cm following a particular exponential equation. However, the targets shot at the shortest distance (10cm) did not satisfy the above equation, probably due to the noticeable differences of the GSR-pattern of these targets (e.g. high presence of soot). Then, the equation was applied to validation samples to estimate the shooting distances, obtaining results with an error below 10%.
在400 - 1000nm范围内的18个特定波长下，记录了在七个不同距离（从10到220厘米）拍摄的衣物目标的多光谱图像，以可视化枪击残留物（GSR）模式。主成分分析（PCA）表明，使用紫蓝色波长（430、450和470nm）时，GSR颗粒与白色棉织物之间的对比度最大。然后，研究了衣物目标上GSR颗粒数量与射击距离之间的相关性。通过选择多光谱图像的蓝色帧（即红绿蓝（RGB）系统中位于470nm处的蓝色帧），基于该帧中像素的强度计算包含GSR颗粒的像素数量。结果表明，从30到220厘米的射击距离内，包含GSR颗粒像素数量按照特定指数方程随射击距离呈指数下降。然而，在最短距离（10厘米）射击的目标不满足上述方程，可能是由于这些目标的GSR模式存在明显差异（例如烟灰大量存在）。然后，将该方程应用于验证样本以估计射击距离，得到的误差低于10%的结果。
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