[4C1] Forensic crime scene investigation in daylight conditions for the detection of time-sensitive low-level fluorescent evidence
G Diamond
Inspection Tech Ltd, UK
This paper presents a lock-in detection machine vision non-destructive testing (NDT) system that overcomes one of the biggest problems of forensic crime and fire scene investigation – the detection of low-level fluorescence from evidence without the need for darkroom/night-time conditions. This system is also backed by software that automatically detects, sizes and records even the weakest of fluorescent indications and alerts the user to their presence under conditions that would make it extremely difficult, if not impossible, for a human investigator to detect them.
Fluorescent light sources (FLSs) are widely used in investigations of crime scenes and sites of fires to detect the fluorescent signatures of body fluids, bone/teeth fragments, accelerants and narcotics. Currently, due to the low levels of fluorescence involved, it is often necessary to perform such investigations under dark room conditions while indoors and at night while outdoors.
This can lead to investigation delays in the detection of time-sensitive evidence due to the requirement for dark conditions, which can also necessitate the construction of tents and awnings and reduction of the working area. Moreover, reliance on human investigators also means that attention span and skill levels are subjective and variable, resulting in quality standard inconsistencies and sometimes the failure to detect evidence altogether.
The NDT solution presented here is a machine vision system that can abstract extremely low levels of fluorescence (<20 lux) from background light levels in excess of 100,000 lux. There is no need for the user to manually illuminate the scene with a range of auxiliary light sources, nor resort to using optical filters, as the system has self-contained light sources (365, 455, 530, 590, 400, 505 and 625 nm) and in-built digital filtering. (It also provides the advantage of not always having to sift through ashes at fire scene investigations to detect bone fragments as they can be detected in situ with the system.)
All scans of a scene under bright light conditions have a photographic map of the fluorescent indications overlaid, for 100% quality assurance (QA) and evidence recording purposes.
Fluorescent light sources (FLSs) are widely used in investigations of crime scenes and sites of fires to detect the fluorescent signatures of body fluids, bone/teeth fragments, accelerants and narcotics. Currently, due to the low levels of fluorescence involved, it is often necessary to perform such investigations under dark room conditions while indoors and at night while outdoors.
This can lead to investigation delays in the detection of time-sensitive evidence due to the requirement for dark conditions, which can also necessitate the construction of tents and awnings and reduction of the working area. Moreover, reliance on human investigators also means that attention span and skill levels are subjective and variable, resulting in quality standard inconsistencies and sometimes the failure to detect evidence altogether.
The NDT solution presented here is a machine vision system that can abstract extremely low levels of fluorescence (<20 lux) from background light levels in excess of 100,000 lux. There is no need for the user to manually illuminate the scene with a range of auxiliary light sources, nor resort to using optical filters, as the system has self-contained light sources (365, 455, 530, 590, 400, 505 and 625 nm) and in-built digital filtering. (It also provides the advantage of not always having to sift through ashes at fire scene investigations to detect bone fragments as they can be detected in situ with the system.)
All scans of a scene under bright light conditions have a photographic map of the fluorescent indications overlaid, for 100% quality assurance (QA) and evidence recording purposes.
