We have combined the basic human ability to recognize other individuals with functional anatomical and biomechanical
knowledge, in order to analyze the gait of perpetrators as recorded on surveillance video. The perpetrators are then
compared with similar analyses of suspects. At present we give a statement to the police as to whether the perpetrator
has a characteristic gait pattern compared to normal gait, and if a suspect has a comparable gait pattern. We have found
agreements such as: limping, varus instability in the knee at heel strike, larger lateral flexion of the spinal column to one
side than the other, inverted ankle during stance, pronounced sagittal head-movements, and marked head-shoulder
posture. Based on these characteristic features, we state whether suspect and perpetrator could have the same identity
but it is not possible to positively identify the perpetrator. Nevertheless, we have been involved in several cases where
the court has found that this type of gait analysis, especially combined with photogrammetry, was a valuable tool. The
primary requisites are surveillance cameras recording with sufficient frequency, ideally about 15 Hz, which are
positioned in frontal and preferably also in profile view.
Since the 1990s photogrammetry has been used in forensic medicine to help identifying perpetrators from crime scenes
covered with surveillance video. Some case studies [1,2] have shown promising results measuring both heights and
segment lengths. Photogrammetry is used with high precision when measuring clearly defined points but less is known
about the reproducibility of hidden body-points. In this study we quantified the inter- and intra-observer variability of
bodily measures with the software PhotoModeler Pro in low resolution images. The study showed that the body height
and shoulder height were reproducible within ± 1 cm and ± 2 cm respectively. The measurement error were markedly
higher for all measurements between points hidden by clothes and measurements of segment lengths were only usable in
the intra-observer situation when flexion in the joints were present. In the inter-observer study the measurement error
was so high that few measurements could be used beside shoulder and body height. Measurements are suggested to be
done with the perpetrator and suspect in the same pose.
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