Forensic crime scene investigation in daylight conditions for the detection of time-sensitive, low-level fluorescent evidence

Abstract

We present a lock-in detection machine vision 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 backed by software that automatically detects, sizes and records even the weakest of fluorescent indications and alerts the user to their presence under conditions which would make it extremely difficult ‐ if not impossible- for a human investigator to detect. Fluorescent light sources (FLS) 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 whilst indoors and at night whilst 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 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 system contains a range of inbuilt, self-contained light sources (365, 455, 530, 590, 400,505 and 625) nm and in-built digital filtering. Moreover, there is no need to resort to multiple colour filters as digital RGB colour-space is implemented. (It also provides the unique 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 upon them, for a 100% QA and evidence recording purposes.