Bacci Nicholas, Briers Nanette, Steyn Maryna
Human Variation and Identification Research Unit, School of Anatomical Sciences, University of the Witwatersrand, Johannesburg, South Africa.
J Forensic Sci. 2021 Jul;66(4):1220-1233. doi: 10.1111/1556-4029.14722. Epub 2021 Apr 22.
Disguises are commonly used to mask a person's facial appearance in areas under closed-circuit television (CCTV) surveillance. While many studies attempted to understand the effects of disguises, such as hats and glasses, on facial recognition, limited studies have looked at disguises in forensic facial comparison. The aim of this study was to compare the outcomes of forensic facial comparison by morphological analysis (MA) in a CCTV sample with sunglasses and brimmed caps. The sample was obtained from the Wits Face Database and organized into 81 face pools of one target facial image wearing a disguise (cap or sunglasses) and 10 potential matching images. MA was conducted across face pools, and confusion matrices were used to assess the outcomes. Surprisingly, sunglasses had limited effect on MA performance both in accuracy (90.4%) and in reliability (κ = 0.798), while caps markedly decreased both accuracy (68.1%) and reliability (κ = 0.639). Error rates were associated primarily with false negatives in both samples (caps: 42.4%; sunglasses: 16.1%) despite the sample distribution favoring false-positive errors, which were very low (caps: 0.6%; sunglasses: 0%). Similarly to other studies, hats and caps were more harmful to correct identification when compared to sunglasses, which actually resulted in better accuracy than regular CCTV recordings. The effect of brimmed caps on accuracy was attributed to the overall loss of facial information caused. On training analysts, it may be helpful to instruct purposefully avoiding overreliance on easily disguised facial features, as other regions of the face also contain substantial feature information.
在闭路电视（CCTV）监控区域，伪装通常用于掩盖人的面部外观。虽然许多研究试图了解帽子和眼镜等伪装对面部识别的影响，但在法医面部比对中研究伪装的却很少。本研究的目的是通过形态分析（MA）比较闭路电视样本中戴太阳镜和帽檐帽的法医面部比对结果。样本取自威特斯面部数据库，分为81个面部组，每组包含一张戴伪装（帽子或太阳镜）的目标面部图像和10张潜在匹配图像。对各面部组进行了形态分析，并使用混淆矩阵评估结果。令人惊讶的是，太阳镜对形态分析性能的准确性（90.4%）和可靠性（κ = 0.798）影响有限，而帽子则显著降低了准确性（68.1%）和可靠性（κ = 0.639）。尽管样本分布有利于假阳性错误（非常低，帽子：0.6%；太阳镜：0%），但两个样本中的错误率主要与假阴性相关（帽子：42.4%；太阳镜：16.1%）。与其他研究类似，与太阳镜相比，帽子和帽檐帽对正确识别的危害更大，实际上太阳镜的准确性比常规闭路电视记录更好。帽檐帽对准确性的影响归因于所造成的面部信息整体损失。在培训分析人员时，有针对性地指导他们避免过度依赖容易被伪装的面部特征可能会有所帮助，因为面部的其他区域也包含大量的特征信息。
