As forensic science technologies progress, digital photography in the crime scene documentation is being replaced in favor of high-precision 3D measurements. Three-dimensional documentation presents every object in the context of the entire crime scene and allows accurate measurements between potentially important traces, like bloodstains or weapons. These and other advanced 3D documentation and analysis tools have improved the possibilities of investigation to a previously unattainable level. We present a novel solution for detailed 3D documentation, which overcomes the limitations of commonly used 3D measurement techniques, e.g. highly accurate Structured Light Scanning or convenient to use Structure from Motion. Our solution, called active-SfM, involves the use of special projection devices to project a random pattern on the part of the scene under measurement. This modification makes the measurement process robust and reliable, even when measuring featureless surfaces. The reconstructed 3D model has better quality and surface uniformity than the result of standard Structure from Motion measurements. Moreover, the acquisition process remains as quick and easy to use as before the modifications.
We present newly developed equipment: wireless projection devices and controllers, that were designed especially to be used by forensic technicians on crime scenes and that are compatible with stock cameras used by them in everyday practice. We also present a full set of developed algorithms that transform input images into the final 3D model.
The proposed solution complements the hierarchical, three-dimensional measurement system developed in recent years by Polish Central Forensic Laboratory of the Police, CYBID Ltd., and Warsaw University of Technology, designed especially for crime scene documentation. The whole documentation process is supervised by a specialized CrimeView3D application, a software platform for measurement management and data visualization. We also present the outcome of measurement sessions that were conducted on both simulated and real crime scenes with the cooperation of Technicians from Central Forensic Laboratory of Police.
Three dimensional measurements (such as photogrammetry, Time of Flight, Structure from Motion or Structured Light techniques) are becoming a standard in the crime scene documentation process. The usage of 3D measurement techniques provide an opportunity to prepare more insightful investigation and helps to show every trace in the context of the entire crime scene. In this paper we would like to present a hierarchical, three-dimensional measurement system that is designed for crime scenes documentation process. Our system reflects the actual standards in crime scene documentation process – it is designed to perform measurement in two stages. First stage of documentation, the most general, is prepared with a scanner with relatively low spatial resolution but also big measuring volume – it is used for the whole scene documentation. Second stage is much more detailed: high resolution but smaller size of measuring volume for areas that required more detailed approach. The documentation process is supervised by a specialised application CrimeView3D, that is a software platform for measurements management (connecting with scanners and carrying out measurements, automatic or semi-automatic data registration in the real time) and data visualisation (3D visualisation of documented scenes). It also provides a series of useful tools for forensic technicians: virtual measuring tape, searching for sources of blood spatter, virtual walk on the crime scene and many others. In this paper we present our measuring system and the developed software. We also provide an outcome from research on metrological validation of scanners that was performed according to VDI/VDE standard. We present a CrimeView3D – a software-platform that was developed to manage the crime scene documentation process. We also present an outcome from measurement sessions that were conducted on real crime scenes with cooperation with Technicians from Central Forensic Laboratory of Police.