Predicting alternate light absorption in areas of trauma based on degree of skin pigmentation: Not all wavelengths are equal.

Detection and documentation of bruises on survivors of intimate partner violence (IPV) can provide valuable evidence to support investigation and subsequent prosecution of these crimes. Detection of bruises in persons with darker skin tones is often difficult, contributing to disparities in health and criminal justice responses to IPV. The purpose of this secondary data analysis was to determine whether use of an alternate light source (ALS) increased the predictive probability of successfully detecting bruises on diverse skin tones following a history of physical trauma. In this study, data were analyzed from a convenience sample of 157 subjects inclusive of six skin tones (very light, light, intermediate, tan, brown, dark) with induced bruises. Bruises were assessed under white light and an ALS 21 times over four weeks using 10 different ALS wavelength and goggle color combinations. Data analyzed included 31,841 skin observations obtained over 2897 participant assessments. Multilevel modeling was used to account for the correlation among the repeated measurements for each bruise. Across all categories of skin pigmentation, ALS wavelengths 415 nm and 450 nm viewed through a yellow filter had the most frequent detections of bruises (415 nm: n = 2777, 11.2%; 450 nm: n = 2747, 11.1%) and greater predictive probability of a positive finding (415 nm: 0.90-0.99; 450 nm: 0.85-0.99) than white light (n = 2487; 10%; 0.81-0.90). These two ALS wavelengths were the only combinations that provided greater probability of detection than white light on groups with darker skin (brown or dark), whereas additional ALS wavelengths/filters worked equally well on groups with lighter skin. Findings suggest use of an ALS in clinical assessments of patients of color who report IPV may help reduce health and criminal justice-related disparities.

Noninvasive, visual examination for the presence of gunshot residue on human skin.

When a firearm is discharged, the highest concentration of gunshot residue (GSR) is located on a shooter's hands, forearms, and clothing. Currently, collecting GSR from an individual's hands is accomplished with a carbon disk that is submitted for confirmatory analysis in a forensic laboratory. Presumptive chemical tests can be performed in the field, but these tests consume a portion of the GSR particles leaving a reduced amount of evidence available to be collected and sent to a forensic laboratory. An abundance of research exists for detecting GSR particles instantly on different fabrics using an alternate light source (ALS). This study expanded on that research and developed a noninvasive, visual examination to detect GSR on a suspected shooter's hands without destroying or removing any particles prior to collection. The hands of individuals who recently discharged a firearm were examined under a light source between 475 and 530 nm and an infrared (IR) camera. The fluorescent particles observed on a shooter's hands under 520 nm were similar in size and appearance to GSR particles observed on fabrics under an ALS. The fluorescent particles were collected and analyzed for GSR, and the results indicated that GSR particles were present. More testing needs to be conducted to determine if the fluorescent particles observed are inorganic or organic GSR particles. There is also potential to detect GSR under IR light; however, more research needs to be conducted to determine the composition of the particles observed after image enhancement.

Degrees of contrast: Detection of latent bloodstains on fabric using an alternate light source (ALS) and the effects of washing.

Blood is often a piece of evidence of violent crimes and will often be on the perpetrator's clothing. If the perpetrator is wearing dark clothing, it can be easily identified by chemical means such as Bluestar®, but this can destroy the pattern, which may be evidentiary itself. This study explores the use of alternate light source (ALS) to photograph bloodstains on dark and/or patterned fabrics to provide an alternate, noninvasive tool before the use of chemical detection techniques. Sixty-nine (69) unwashed fabrics, of various dark colored and dark patterns, were photographed in monochrome under ambient light and subsequently with and without a filter under ultraviolet (UV), violet, blue, green, and infrared light. This study used ImageJ to measure the contrast between the bloodstain and the fabric and thus the effectiveness of each wavelength. Each fabric was washed, photographed, and analyzed five times or until the bloodstain was no longer visible under ALS. Results indicated photography with ALS was a viable method for blood detection on fabrics and should be used prior to chemical means. Further, infrared, followed by violet light with no filter, was the most effective light source for viewing bloodstains on dark fabrics without the use of chemicals. However, these wavelengths were not effective on military uniforms. This study also described one effect fabric manufacturer chemical treatments have on bloodstains and the effect of washing fabrics with bloodstains.

Recovery of trace evidence in forensic archaeology and the use of alternate light sources (ALS).

The effectiveness of alternate light source (ALS) to fluoresce bone and other materials is well-attested to in a laboratory setting but rarely, if ever, has it been used in field excavation. This study examined the recovery rates of fragmentary bone, fabric, and metal, both with and without the use of an ALS, through practical and controlled excavation experiments with multiple users. All archaeology, including forensic archaeology and crime scene investigation more generally, should account for trace evidence. Currently, there is limited empirical data for the recovery of evidence from excavation, and those studies that do exist, highlight the short-comings in current methods. Six comparable test pits were created, representing empty graves in which only trace evidence remained. Each contained 20 fragments of bone (≤10mm), 16 hair fibres, two pieces of fabric and two lead pieces, which were back-filled and left for over 15 weeks. Three excavators were each tasked with excavating two test pits: one using ALS, one in daylight conditions. The results of the experiment identified some critical aspects of using blue 455nm wavelength ALS in the field, and the importance of experienced practitioners. Sample evidence was small in size and recovery rates were low. In daylight conditions, an average of 46% of trace evidence was identified, while just 40% was recovered using ALS. This excludes hair fibres which were almost undetectable in all conditions. When using ALS, smaller bone fragments were more than twice as likely to be recovered, but less non-fluorescent materials were found. The experience of each excavator had a positive correlation with excavation results. Excavation error rates were calculated, demonstrating that excavation is comparable using either technique, but daylight conditions lead to greater accuracy. The findings suggest that ALS can be used to increase recovery of some evidence types. Test pits provided none of the usual primary evidence associated with graves and excavators had no prior experience of ALS. While retrieval rates were low, almost all recovered items were found in situ and an accurate records maintained. Error rates in forensic archaeology are essential and it is hoped that the method outlined here can be developed towards the establishment of acceptable error rates. While ALS use in forensic archaeology should not be considered a panacea to issues of trace evidence recovery, a combination of well-tested archaeological excavation methods, alongside the implementation of such proven forensic techniques, would likely lead to improved recovery of evidence.

Evaluation of a model of bruising in pigmented skin for investigating the potential for alternate light source illumination to enhance the appearance of bruises by photography of visible and infrared light.

The purpose of this study was to evaluate the ability of alternate light source illumination to enhance bruises in pigmented skin. Previous work was limited to simulating bruises in non-pigmented (Caucasoid type) skin by injecting blood into pigskin. In this study, it was investigated if adding a layer of melanin to the surface of the skin would simulate pigmented skin. The study included evaluating the use of a filter that transmitted infrared light (wavelength greater than 720 nm) in place of the recommended visible light filters for the alternate light sources. The results obtained using pigskin with a layer of melanin were almost the same as results using the naturally pigmented goat ear. This indicated adding a layer of melanin could be used as a model for pigmented skin in this simulation of fresh bruising. Comparing the pigskin without melanin with pigskin with melanin revealed that the optimal light source to enhance the appearance of bruising, simulated by injection of blood, changed from violet to blue-green. Using the infrared transmitting filter resulted in greater enhancement than using the alternate light sources with their recommended visible light filter. The advantage of using the infrared transmitting filter was greater with the pigskin coated with melanin and the naturally pigmented goat ears than in the non-pigmented pigskin, however, the results remain to be validated using real bruises in naturally pigmented human skin.

Repeatedly washed semen stains: Optimal screening and sampling strategies for DNA analysis.

In many sexual assault cases, bedding and clothing are essential pieces of evidence that are screened for semen stains to gather DNA from the assailant. In some cases, these items have been washed before being seized and sent to the forensic lab. However, few data exist on the optimal methods for detecting and sampling semen stains on washed fabrics. In this paper, we used semen stains washed up to six times to evaluate the efficiency of commonly used screening methods for the detection of semen: alternate light source (ALS), acid phosphatase (AP), prostate specific antigen (PSA) and microscopy (sperm Hy-Liter™, SHL). We also assessed different washing conditions (detergents, washing machines, addition of bleach) and sampling methods (cutting and swabbing). The results show that some semen stain detection strategies, such as ALS, PSA, and SHL, are effective even when the item was washed multiple times. We also show that a complete genetic profile could be obtained from semen stains washed six times. Based on these findings, we present different strategies for the detection and sampling of semen stains depending on the circumstances of the case.

Is the visibility of standardized inflicted bruises improved by using an alternate ('forensic') light source?

AIM: To study the visibility of standardized inflicted bruises by using an alternate ('forensic') light source compared to a white light source. METHODS: Bruises were inflicted on the flexor site of the forearm (halfway in the middle) in 76 adults, by suddenly allowing a cylindrical metal object (400g) with rounded edges to drop for 1m in a vertically positioned tube. At 0.25, 1, 2, 7 and 14days after this blunt force impact, the impact site on the forearm was photographed with a white light source and subsequently with an alternate light source at 415nm. Visibility of bruises on 170 randomized photographs was assessed on a calibrated monitor by 10 forensic medical specialists (physicians and pathologists) independently in two sessions: (1) with white light source photographs, and (2) after a mean of 11days with greyscale converted alternate light source photographs. Bruise visibility was expressed as a report mark between 1 (very bad) and 10 (excellent), or as 'no visible bruise'. To determine intra-rater agreement, 10 of 170 photographs were assessed twice (untold to the assessors). In total 3600 (180×10×2) photographs were assessed. RESULTS: 39 of 73 (53%) participants who completed the study, developed a visible bruise (women more often than men, p<0.001). Inter-rater agreement between assessors was high (mean inter-class coefficient, ICC, for white light source 0.66 (SD 0.14) and for alternate light source ICC 0.73 (0.09)). Intra-rater agreement was excellent (mean ICC 0.88 (SD 0.09)). Mean report marks for bruise visibility, recorded independently by 10 assessors on 170 unique photographs per light source, were significantly higher with an alternate light source than with a white light source, at 1 and 2days after impact: 4.4 (SD 2.0) vs 3.8 (1.8) (p<0.01) and 4.9 (2.1) vs 4.5 (2.0) (p<0.05), respectively. However, these differences were small, as the mean difference (effect size) in report marks were 0.6 (0.5) and 0.4 (0.3), at 1 and 2days after impact, respectively. The other time points showed no statistical significant differences in report marks. CONCLUSIONS: Bruises after standardized blunt force impact were slightly better visible with an alternate light source than with a white light source after 1 and 2 days, but not after 0.25, 7 and 14 days. The value of using an alternate light source at 415nm to improve bruise visibility was limited in this study.

The adaptation of a 360° camera utilising an alternate light source (ALS) for the detection of biological fluids at crime scenes.

One of the most important and commonly encountered evidence types that can be recovered at crime scenes are biological fluids. Due to the ephemeral nature of biological fluids and the valuable DNA that they can contain, it is fundamental that these are documented extensively and recovered rapidly. Locating and identifying biological fluids can prove a challenging task but can aid in reconstructing a sequence of events. Alternate light sources (ALS) offer powerful non-invasive methods for locating and enhancing biological fluids utilising different wavelengths of light. Current methods for locating biological fluids using ALS's may be time consuming, as they often require close range searching of potentially large crime scenes. Subsequent documentation using digital cameras and alternate light sources can increase the investigation time and due to the cameras low dynamic range, photographs can appear under or over exposed. This study presents a technique, which allows the simultaneous detection and visualisation of semen and saliva utilising a SceneCam 360° camera (Spheron VR AG), which was adapted to integrate a blue Crime Lite XL (Foster+Freeman). This technique was investigated using different volumes of semen and saliva, on porous and non-porous substrates, and the ability to detect these at incremental distances from the substrate. Substrate type and colour had a significant effect on the detection of the biological fluid, with limited fluid detection on darker substrates. The unique real-time High Dynamic range (HDR) ability of the SceneCam significantly enhanced the detection of biological fluids where background fluorescence masked target fluorescence. These preliminary results are presented as a proof of concept for combining 360° photography using HDR and an ALS for the detection of biological stains, within a scene, in real time, whilst conveying spatial relationships of staining to other evidence. This technique presents the opportunity to presumptively screen a crime scene for biological fluids and will facilitate simultaneous location and visualisation of biological evidence.

Use of an Alternate Light Source to Detect Tooth and Bone

Resumo O objetivo desse trabalho foi identificar a combinação do comprimento de onda e filtro que melhor detecta dente e osso e verificar qual material biológico (esmalte, raiz dental ou osso) possui maior fluorescência quando exposto a uma fonte de luz alternativa (ALS). Amostras de dente e osso foram iluminadas com uma ALS e fotografadas. Os programas Adobe Photoshop™ e ImageJ™ foram usados para análise das imagens. Os dados obtidos das medidas dos pixels das fotografias foram submetidos a análise de variância. Os valores com efeitos significativos tiveram suas médias comparadas pelo teste de Tukey. Em todos os testes, o nível de significância adotado foi p≤0,05 e os valores calculados pelo sistema SAS. Os resultados mostraram que a melhor combinação para detectar dente e osso é o comprimento de onda 455 nm com o filtro laranja. A fluorescência da raiz é maior que a do esmalte que é maior do que o osso. O material biológico teve maior fluorescência que o material inerte. Esse conhecimento pode auxiliar o perito a triar e detectar esses materiais biológicos, por exemplo em situações em que dentes e pequenos ossos estiverem fragmentados, tanto na cena do crime quanto no laboratório.

Abstract The aim of this study was to identify the combination of wavelength and filter that best detects tooth and bone, and to determine which biological materials (enamel, dental root or bone) have highest fluorescence intensity when exposed to an alternate light source (ALS). Tooth and bone samples were lighted with ALS and photographed. Adobe Photoshop™ and ImageJ™ softwares were used for image analysis. Data obtained by measuring the photograph pixels were subjected to analysis of variance. The mean values of significant effects were compared by the Tukey test. In all tests, the significance level was set at p≤0.05 and the values calculated by the SAS system. The results showed that the best combination for detecting tooth and bone is an illumination wavelength of 455 nm with an orange filter. The fluorescence of dental root is greater than that of enamel, which in turn is greater than that of bone. The biological material had markedly higher fluorescence than the inert material. This knowledge can help the forensic expert to screen and detect biological materials, for example in situations where there are fragmented teeth and small bones, both at the scene and in the laboratory.

The Effect of Time on Bone Fluorescence: Implications for Using Alternate Light Sources to Search for Skeletal Remains.

Bones fluoresce when exposed to certain wavelengths of shortwave light, and this property can be useful in locating and sorting skeletal remains in forensic contexts. The proteins in bone collagen are largely responsible for its fluorescent properties, but these proteins degrade and denature over time. This study examined the fluorescence of bones from four temporal groups (recent, semi-recent, ancient, and historic) ranging from 0 to 1064 years before present. Specimens were photographed under 490 nm wavelength light, and fluorescence was quantified by converting intensity to a gray scale value based on the RGB color model using ImageJ(®) software. Significant (p < 0.05) differences were found in mean fluorescence between all four temporal groups, and a 0.324 coefficient of correlation indicates a significant (inverse) relationship between fluorescence and time. Bone fluorescence decreases with time, but some fluorescence is retained even in older samples. Fluorescence can therefore be reliably used in many modern skeletal remains searches.

The application of imaging technologies in the detection of trace evidence in forensic medical investigation.

In a country notorious for violent crime, it seems that South African medico-legal laboratories make minimal application of technology in the death investigation process and little attention is given to trace evidence. Non-destructive, non-invasive, portable and cost-effective tools are required. This study was conducted at the Pretoria Medico-Legal Laboratory. The surface area of the bodies and clothing of victims of fatal interpersonal violence were examined using a torch, magnifying lamp, portable digital microscope and alternate light source to gauge their potential for trace evidence detection. Most studies apply these and similar tools to inert surfaces, with few focusing on their application to human skin. There was a statistically significant difference in the detection of many of the evidence types between the naked-eye observation of the pathologists and the technologies. The different imaging technologies were compared as to their cost, evidence detection ability and ease of use. The most common evidence types discovered on the bodies and clothing of victims of fatal interpersonal violence, as well as the propensity of each tool to detect these, was evaluated in order to devise the best option for incorporation into the Pretoria Medico-Legal Laboratory routine. The digital microscope performed best overall followed by the magnifying lamp, torch and the Polilight(®). This study aimed to justify the investment of more time, effort and funding into trace evidence recovery in the South African mortuary environment.

The use of an alternate light source for detecting bones underwater.

When searching underwater crime scenes or disaster scenes for fragmentary human remains, it may be advantageous for forensic divers to be able to detect the presence of bones and teeth among other marine materials (such as shells and rocks). In terrestrial environments, this can typically be accomplished by visual and instrumental methods, but underwater conditions make it difficult to employ detection and sorting techniques in these environments. This study investigates fluorescence of bones and teeth and other marine materials using a submersible alternate light source (ALS) and concludes that an ALS can be a useful tool for detecting bones and teeth in underwater searches as well in terrestrial searches and laboratory environments. The results could impact the methods and equipment used by forensic divers and forensic anthropologists when searching for skeletal remains, potentially increasing the quantity and efficiency of forensic evidence recovered.

Using an alternate light source to detect electrically singed feathers and hair in a forensic setting.

Mortality due to electrical injury in wildlife may occur in the form of lightning strike or power line contact. Evidence of electrical contact may be grossly obvious, with extensive singeing, curling, and blackening of feathers, fur, or skin. Occasionally, changes may be subtle, owing to lower current or reduced conductivity, making a definitive diagnosis of electrocution more difficult. We describe the use of an alternate light source in the examination of cases of lightning strike and power line contact in wildlife, and the enhanced detection of changes due to electrical currents in the hair and feathers of affected animals. Subtle changes in the wing feathers of 12 snow geese and 1 wolf that were struck by separate lightning events were made obvious by the use of an alternate light source. Similarly, this technique can be used to strengthen the evidence for power line exposure in birds.