The effect of viewing angle on observations of foot orientation in forensic gait analysis

Forensic gait analysis is the analysis, comparison and evaluation of features of gait to assist in the investigation of crime. Analysis refers to the process of observing features of gait and assessing their reliability for use in comparison, within the limitations of the quality of the footage. Forensic gait analysis often uses closed circuit television (CCTV) cameras to view the figure of interest. A limitation associated with using CCTV cameras is the viewing angle provided of the figure of interest. The aim of this study was to test the effect of viewing angle on observations made about the orientation of a figure’s feet whilst the figure was walking. The results will supplement the forensic gait analyst’s understanding of uncertainty measures. An opportunistic sample of 31 participants, with some knowledge of observational gait analysis, was recruited. Each participant viewed nine clips of an Avatar walking with its feet abducted to 30 degrees. Viewing angles ranged from 0 degrees to 180 degrees in 22.5 degree increments from the Avatar’s left side. Participants were asked to comment on the orientation of both the left and right feet. The most reliable viewing angle to make judgements about the orientation of the feet was in the frontal plane, from the rear of the avatar. The most unreliable viewing angle was obliquely, from the front and side of the avatar. More incorrect judgements were made about the foot situated furthest from the camera, than the foot closest to it. Viewing angle relative to the figure being observed can influence judgements about angle of gait, and practitioners should be mindful of this when analysing, comparing and evaluating this feature as part of forensic gait analysis.