3D hyperspectral Ladar for forensinc and crime scene investigation – SHERLOC

In close collaboration with IRCGN and SDPTS, the consortium has compiled a list of traces or sensitive substances to be detected. A laboratory study was conducted based on passive hyperspectral imaging to identify spectral domains of interest. Alternative methods (UV fluorescence and polarimetric imaging were also evaluated). At the end of the laboratory study, a large number of possible methods of detection were considered pertinent. It was necessary to select the most relevant to design a demonstrator in the time allowed. In order to reduce the number of laser sources and detectors, we have restricted ourselves to a single spectral domain (the one that allowed the greatest number of traces to be visualized). A broadband laser source illuminates the scene point by point, and for each point, the backscattering spectrum of the light is collected. A hyperspectral image of the scene is then obtained. EXAVISION then developed a demonstrator. The latter was evaluated under operational conditions by the IRCGN and the SDPTS. Throughout the project, the ICP assessed the legal impacts of the SHERLOC prototype.

Fine numerical treatments can detect different biological traces (blood, urine, sperm, saliva, blood), narcotics and, to a lesser extent, ballistic traces. A laser pointer makes it possible to locate the possible anomaly so that the technicians take samples for further analysis. The prototype was tested by the IRCGN and SDPTS and was considered promising. The ICP study founds no contradiction to the use of SHERLOC from a legal point of view.

The SHERLOC study demonstrated the contribution of hyper-spectral imaging for the detection of biological traces on a crime scene. Technological locks led us to give up the complete geo-referencing of detected traces. This is dependent on the fact that there is not yet gated spectrometer “off the shelf”. In the near future, this lock should be resolved and should allow for significant progress. In the short term, one of the objectives is to gain in compactness thanks to this accessible technological maturation. The alternative tracks of detection of papillary traces are very promising and should be the subject of a specific development. In addition, SHERLOC provides a new means of measuring hyperspectral signatures that can be used in a wide range of fields other than forensic.

Since the beginning of the project, the results have been presented to the various WISGs (2013, 2014, 2015 and 2016). We are currently investigating possible publications in optics journals and more forensic-oriented journals.

Today, many crimes or offences are resolved by the police using Science and Forensic expertise has benefited from significant technological advances. However, it remains a real need to provide forensic services with innovative tools that could be used to improve a quick and remote detection of multiple markers or clues (papillary, biological, chemical, organic ) avoiding intrusions in the crime scene that could interfere with the proceedings. While the complexity of detection is increasing by the multitude of clues, it is also made more and more difficult by the nature of the scene (e.g. measuring outdoor or analysis of an indoor scene that was "contaminated or cleaned" by the perpetrators). Today, in support of protocols and their experiences, the forensic experts have tools to detect these markers, which are often separated (one by an average trace) and are limited by the remote detection of complex cases mentioned above. A unique tool able to provide an improved detection could offer operational gains to criminologist and forensic service and limit the loss of useful clues. The Sherloc project includes two referents forensic services in France and offers an innovative approach based on 3D and hyperspectral laser imaging combined with image processing. It will provide a practical solution offering remote detection (possibly classification) and localization of clues in many scenes of crime. This project involves Onera for the development of the system and image processing methods with EXAVISION, an SME, for the operational design of the demonstrator and the Institute of Crime in Paris to study the impact on the constitution of the evidence. This project will provide to the French forensic services fully involved, a demonstrator corresponding for their needs and expectations, through an Industrial Research.