CRIME-LITE APPLICATIONS //
Utilising Crime-lites for the visualisation of fluorescence from STK Sperm Tracker™
A collaborative study between foster+freeman and L’Institut de Recherche Criminelle de la Gendarmerie Nationale (IRCGN).
Background
Introduction
The identification of a body fluid detected on a piece of forensic evidence can be critical to an investigation. Identification of the location of a body fluid not only allows forensic scientists to perform crime scene reconstructions but also provides further support in identifying the most appropriate samples for DNA analysis.
STK SPERM TRACKER™
STK Sperm Tracker™ was developed in a collaboration between AXO Science and the French National Institute of Scientific Police (INPS). Spermtracker technology is commercially available in multiple formats; a lab-based paper or a spray which can be utilised directly at a crime scene or directly on skin. If a semen stain is present on the substrate, a UV-A forensic light source can be applied to visualise the fluorescent emission from the STK paper. A positive result for semen is indicated by a clear and bright-blue fluorescent result on the STK paper. A collaborative study has been conducted alongside L’Institut de Recherche Criminelle de la Gendarmerie Nationale, with the aim to determine whether Foster + Freeman UV Crime-lite light sources are suitable for promoting visualisation of fluorescence from STK paper.
Recommendations
The manufacturer specification recommends that a UV light source with a peak wavelength of 365-366nm should be used to promote fluorescence emission from their STK products. All Crime-lite light sources featured within this study utilise UV with a peak wavelength of 365nm (bandwidth 350-380nm). Samples were initially visually checked throughout the study with the Crime-lite 82S UV light source and then illuminated and imaged with both the Crime-lite AUTO and the Crime-lite ML PRO.
Using the Crime-lite ML PRO to examine semen staining on evidence within the laboratory.
Test Conditions
The study was conducted at foster+freeman Headquarters in Evesham, UK. Ten samples were provided by L’Institut de Recherche Criminelle de la Gendarmerie Nationale for the collaborative study: five single-source samples containing semen on fabric and five mixed-source samples containing semen and blood on fabric. foster+freeman provided a single-source control sample of semen on fabric.
The STK paper was cut to twice the dimensions of the fabric to be analysed. The unplasticised surface of the paper was then wetted uniformly with distilled water using a spray bottle with the paper briefly suspended to remove any excess water. The fabric was placed onto the wetted side of the paper, before the STK paper was then folded in half ensuring the fabric was sandwiched between it. Pressured was applied to the STK paper utilising a weighted object of 5kg and the sample was then left for a period of three minute within the pressurised environment. After the period of three minutes, the weight was removed from the sample and the fabric material was imaged.
The Crime-lite 82S UV light source was utilised first to illuminate the fluorescence emission from the STK paper so a visual assessment could be made as to whether a positive result had been achieved. The samples were then illuminated and imaged with both the Crime-lite AUTO and the Crime-lite ML PRO. The Visible Pass filter (GG420 Long pass) was utilised on the Crime-lite AUTO and the GG420 Long pass filter was applied on the Crime-lite ML PRO to visualise the UV fluorescence being emitted by the STK paper in the images.
Sample Images
Conclusions
All ten samples provided by L’Institut de Recherche Criminelle de la Gendarmerie Nationale produced a fluorescence signal emitted from the semen staining which could be observed when viewed visually with the Crime-lite 82S UV light source and when imaged with the Crime-lite AUTO and the Crime-lite ML PRO. The foster+freeman control sample also provided an observable fluorescence reaction from semen staining when viewed under the same three light sources. Some dark staining was observed upon illumination on some of the semen and blood mixtures, although this did not appear to interfere with the positive results attained from these samples.
When illuminated with a foster+freeman Crime-lite light UV sources (365nm), the fluorescence emission from STK can be visualised either with the naked eye or by utilising a GG420 Longpass filter either in goggle or camera filter format (in the Crime-lite AUTO, the GG420 Longpass is labelled as ‘VIS’).
This small collaborative study provides supporting evidence that the Crime-lite 82S UV, the Crime-lite AUTO and the Crime-lite ML PRO all provide a suitable UV light source (365nm) which can be utilised in conjunction with Spermtracker technology.
Products Featured
Crime-lite® AUTO
The Crime-lite AUTO is the most integrated, comprehensive, and compact forensics digital camera solution in existence. Combining the latest forensic imaging technology with high intensity multi-spectral illumination, the Crime-lite AUTO is a complete solution for the search, detection, and capture of forensic evidence.
Crime-lite® ML PRO
The Crime-lite ML PRO is part of a new generation of evidence screening tools, built to meet the demands of high-throughput forensic laboratories tasked with processing large quantities of evidence. With fully integrated UV-Vis-IR illumination and an ‘intelligent optics’ imaging system, the ML PRO can be used to mark-up evidence, detect the presence of a wide variety of different trace evidence, and can create an integrated examination report ready for court.
