Centro de Documentação da PJ
Analítico de Periódico
CD 335
Optimizing underwater visual records for crime scene investigations in water with clear to reduced visibility [Recurso eletrónico] / R. Paba ..[et al.]
Forensic Science International - Synergy, Vol. 6 (2023), p. 1-4
Ficheiro de 342 KB em formato PDF.
PATOLOGIA FORENSE, LOCAL DO CRIME, MEIO AMBIENTE E O CRIME, RECOLHA DA PROVA, VESTÍGIOS, FOTOGRAFIA POLICIAL
A “crime scene” can be defined as a place where a crime has been committed and forensic evidence may be gathered. However, at some scenes, the “crime scene do not cross” tape cannot be placed, forensic experts cannot attend as direct responders, and evidence can be washed away: when the crime scene happens to occur in a body of water, the investigation process can be extremely complex and the outcome of it highly affected by the limitation of equipment and procedures available. However, with an estimated 236,000 annual drowning deaths worldwide (World Health Organization data 2021) [1], several mass disasters occurring in or caused by bodies of water (i.e., boat sinking, tsunami, flooding), a large number of dangerous water-related sports and the never-ending opportunity to conceal body remains in wells, rivers, lakes, cisterns, aquatic environments are common crime scene scenarios [2]. When human remains are suspected to be in a particular water body or are found floating, underwater, or beached, law enforcement experts – police divers especially – are called to the scene. Such teams will perform a complete investigation, from the planning of the operations based on the available personnel and environmental conditions, to the (search and) recovery of the body, the documentation and the collection of small objects and other helpful evidence field [3,4]. However, despite best efforts, some pieces of evidence may be missed, and in certain circumstances, evidence observed underwater are not retrieved due to a lack of equipment, funds, or to safeguard the safety of the divers. In such cases, the correct scene documentation becomes pivotal for the course of the investigation. In most underwater cases, forensic pathologists and investigators will not experience the actual scene, but will see the human remains and the items connected with the body or the crime only when retrieved by the diving personnel. To complete crime scene reconstruction, forensic pathologists and investigators rely on images, documentation and memories provided by the divers. In these cases, accurate underwater crime scene photography and video become essential for capturing visual records of the scene, which can be analysed or examined later. Photography has been considered a powerful forensic investigative tool since the middle of 1800, and the development of new technologies has expanded its use ever since [5]. In recent years, photography, videography, remote sensing, and artificial intelligence have evolved and are now commonly used in various environments to provide testimony of a wide range of investigations. Notorious historical examples on how photographic, video, and remote sensing images have been used in underwater investigations are the discovery of the Titanic wreck (1985), the Russian submarine Kursk (2011) and USS Monitor (2003); however, underwater video footage also used to investigate suspicious deaths, as was the case with the famous singer Whitney Houston, who was found unresponsive in a bathtub in 2012. During underwater operations, the safety of the divers is of primary importance, with priority consideration taken regarding any hazard that could affect them. However, at the same time, the opportunity for divers to conduct systematic search and produce different type of scene documentation (e.g. sketching, photo, video) which can be used in Court can make the difference between closing a case or a miscarriage of justice. Similarly to human remain recovery and excavation performed in a terrestrial environment, in a forensic investigation carried out in bodies of water, both classical tools and new technologies typically used in archaeology – underwater archaeology in this case – may assist law enforcement in such operations. However, it is essential to remember that divers can operate only for a certain period in an underwater scenario. Divers’ working time is determined by various factors such as the depth of the scene, water temperature, environmental conditions (e.g., visibility, currents, waves), and other stress-related factors that can affect the breathing pattern and, as a consequence, the time to reach the limit of a safe reserve of air in the tank. It’s important to note that as the depth of the intervention increases, dive time and image/document acquisition time become shorter, due to the higher requirement of air supply during the bottom time, alongside the need of longer ascent times to accommodate decompression requirements [6]. Furthermore, it is necessary to consider that several factors affect the collection of video and still photography in underwater crime scenes. A degradation in the visibility of underwater images and video is caused by wavelength-dependent light absorption and scattering. This can affect pattern recognition accuracy and perception. Light absorption and scattering (particles suspended in the water column that cause turbidity) hinder the performance of underwater scene recognition and inspection. Color also degrades as longer wavelengths of light are filtered, with depth being a great contributing factor. Over the last few years, the focus has been on underwater image enhancement and restoration as the two techniques to improve underwater images. These processes have come a long way in enhancing underwater images through dehazing and color correction. However, in certain circumstances, an underwater crime scene has zero visibility, making the investigation much more challenging and dangerous for the divers involved [7]. In such cases, it may be difficult or impossible to capture clear and accurate visual records of the scene, and evidence may be gathered using other methods such as metal detectors or sonar equipment to detect any metallic objects or potential obstacles in the water, or special lighting or flares may be used to illuminate the area.
