Inter observer errors of cast-off stains using FARO zone 3D.

Eugene Liscio, Quan Le

Forensic science international 2022 Jan

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The estimated volume of the swing path is referred to as the Path Volume Envelope (PVE) which defines a volume in space from which the path of a blood-releasing object is contained within. FARO Zone 3D is a software program that allows for the calculation of the PVE; however, there are no current studies which look at how well this method performs across various analysts for a simple, human created cast-off pattern. A total of seventeen participants were provided data for a single cast-off pattern that was produced from human motion using a wooden dowel rod as the "weapon". The known three-dimensional motion of the object which created the cast-off pattern was documented using a motion capture system but remained unknown to the participants. The results show that an approximate maximum width of the PVE of±15 cm is enough to encompass the results of all participants in this study. In addition, the X, Y and Z position of the center of the PVE was found to have a standard deviation of 0.1 cm, 5.1 cm, and 9.9 cm, respectively. The standard deviations of the rotations for the PVE around the horizontal and vertical axes (i.e., yaw and pitch) were found to be 2.6° and 1° respectively. Overall, the combined results of all participants were able to fit within a rectangular prism with an overall width of± 15 cm which appears to be a reasonable value for simple scenarios, since it can define an approximate location from where an object was swung relative to a wall or another object at a crime scene. A PVE of greater or lesser maximum width may be required depending on the complexity of the cast-off pattern, the weapon used, and other factors. Copyright © 2021 Elsevier B.V. All rights reserved.