Contactless Size Reference in Forensic Photography
Design and Verification of the Novel FreeRef-1 System
L.A.H. Schiks (TU Delft - Mechanical Engineering)
M.S. Cook (Universiteit van Amsterdam, TU Delft - Mechanical Engineering)
L.R. Lipman (Student TU Delft)
A.P. van Dijke (Nederlands Forensisch Instituut (NFI), TU Delft - Mechanical Engineering)
K. Hutchinson (TU Delft - Mechanical Engineering)
Paul van den Hoven (Nederlands Forensisch Instituut (NFI))
A.J. Loeve (TU Delft - Mechanical Engineering)
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Abstract
In photographs of evidence in forensic investigations, physical size references (e.g., rulers or stickers) are often placed next to a trace to allow us to take measurements from photos. However, this is laborious and introduces contamination risks. The FreeRef-1 system is a contactless size reference system that allows us to take forensic photographs without having to be close to the evidence, and allows photographing under large angles without losing accuracy. The FreeRef-1 system performance was assessed using technical verification tests, inter-observer checks and user tests with forensic professionals. The results show that the measurements taken with photos using the FreeRef-1 system were at least as accurate as those taken using conventional techniques. Furthermore, with the FreeRef-1 system, even photographs taken under strongly oblique angles provided accurate measurements. The results suggest that the FreeRef-1 system will facilitate photographing evidence even in hard-to-reach places, such as under tables and on walls and ceilings, while increasing the accuracy and speed.
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