The reconstruction of a crime scene through 3D technologies

Abstract

The crime scene is fundamental for an investigation, as essential information about the course of events is usually found here. Thus, it’s important that scenes are documented rapidly, to avoid loss of information. Nowadays, 3D terrestrial laser scanning and photogrammetry are able to accomplish this, creating accurate 3D reconstructions of crime scenes. Through these technologies, it is possible for crime scenes to be conserved as initially found, in the form of dense point clouds. This allows the investigator to virtually revisit the scene, analyse it, and gather new insights about the case. A fictitious crime scene involving a possible sexual assault was created to illustrate the terrestrial laser scanning and photogrammetry techniques in practice. Data was collected with a variety of instruments, and specialised software, mainly Agisoft® Metashape and RiScan Pro, were used to process the data and visualise the results in 3D. Photogrammetry resulted to be a flexible tool to use, since it was capable of reconstructing both the crime scene area in general, but also the small articles of evidence, in great detail and clarity. On the other hand, the specific laser scanner used was better at providing accurate data about the geometry of the area, rather than on the small objects found at the scene. In addition, the former technique proved to be very economical when compared to the latter, whose instrumentation can be very costly to invest in. Therefore, an investigator needs to take into consideration a number of factors prior to determining which technique/s to use at a crime scene. These mainly include the level of detail required, the size of the area under investigation, and the instruments available.