Artigo Doutrinário
ALTERNATE LIGHTS IN MEDICOLEGAL PRACTICE: TECHNICAL FUNDAMENTALS FOR SCREENING STANDARDIZATION AND PROMOTION OF RACIAL EQUITY
Como citar: Zaghetto WDC, Silva BDC. ALTERNATE LIGHTS IN MEDICOLEGAL PRACTICE: TECHNICAL FUNDAMENTALS FOR SCREENING STANDARDIZATION AND PROMOTION OF RACIAL EQUITY. Persp Med Legal Pericia Med. Vol. 11, 2026; 260207.
https://dx.doi.org/10.47005/260207
Recebido em 07/12/2025
Aceito em 25/01/2026
The authors report no conflict of interest.
ALTERNATE LIGHTS IN MEDICOLEGAL PRACTICE: TECHNICAL FUNDAMENTALS FOR SCREENING STANDARDIZATION AND PROMOTION OF RACIAL EQUITY
Resumo
INTRODUÇÃO: Apresentar uma proposta técnica de implementação das Fontes de Luz Alternativa (ALS) como protocolo de triagem pericial no Brasil, visando superar a inspeção visual exclusiva sob luz branca e mitigar a “cegueira diagnóstica” em pessoas negras. MATERIAL E MÉTODO: Estudo teórico-doutrinário fundamentado em análise crítica da literatura e da legislação brasileira. RESULTADOS: A análise demonstra que a alta concentração de melanina reduz drasticamente a sensibilidade da inspeção sob luz branca, enquanto evidências comprovam que as luzes alternativas (415nm-450nm) podem aumentar em até 5 vezes a probabilidade de detecção de equimoses. DISCUSSÃO: Embora o método aumente a sensibilidade, as ALS não são fidedignas para a datação de lesões e apresentam risco de falsos-positivos por interferentes externos como cosméticos, exigindo protocolos específicos de limpeza. CONCLUSÃO: A incorporação das ALS constitui uma estratégia ético-jurídica para a garantia da isonomia processual. Propõe-se sua padronização como etapa obrigatória de triagem para qualificar a prova pericial e efetivar o princípio constitucional da equidade no sistema médico-legal brasileiro.
Palavras Chave: Equidade em Saúde; Medicina Legal; Saúde da População Negra; Equimoses; Luzes Forenses.
Abstract
INTRODUCTION: To present a technical proposal for the implementation of Alternate Light Sources (ALS) as a forensic screening protocol in Brazil, aiming to overcome the exclusivity of visual inspection under white light and mitigate "diagnostic blindness" in Black individuals. MATERIAL AND METHOD: A theoretical-doctrinal study based on a critical analysis of the literature and Brazilian legislation. RESULTS: The analysis demonstrates that high melanin concentration drastically reduces the sensitivity of inspection under white light, while evidence proves that alternate light sources (415nm-450nm) can increase the probability of detecting ecchymoses by up to 5 times. DISCUSSION: Although the method increases sensitivity, ALS are not reliable for the dating of injuries and present a risk of false positives from external interferents such as cosmetics, requiring specific protocols. CONCLUSION: The incorporation of ALS constitutes an ethico-legal strategy to guarantee procedural equality. Its standardization is proposed as a mandatory screening stage to qualify forensic evidence and uphold the constitutional principle of equity within the Brazilian medicolegal system.
Keywords (MeSH): Health Equity; Forensic Medicine; Health of Black People; Ecchymosis; Alternate Light Sources.
1. INTRODUCTION
Demographically, Brazil defines itself as a predominantly Black nation. More than 55% of the population self-identifies as Black (preto – 10.2%) or Brown (pardo – 45.3%), according to data from the 2022 Demographic Census(1). This majority is, concurrently, the group most severely impacted by violence, representing 76.5% of homicide victims in the country(2). This characteristic persists when stratifying forms of violence: Black victims are the majority among LGBTQIAPN+ individuals (55.6% Black), in assaults against the elderly — the hospitalization rate for assault for Black elderly men was 16.6 per 100,000 (compared to 8.1 for non-Blacks) and 5.1 for Black elderly women (compared to 2.5 for non-Blacks) — and in domestic violence against women (58.2% of victims are Black)(2). Given that the majority of trauma victims have skin with a high melanin concentration, the adaptation of diagnostic tools becomes a public health imperative. Ecchymosis, the cardinal clinical sign of blunt trauma, plays a central role in the materialization of violence(3). However, traditional medical semiology, based on visual inspection under white light, faces a biophysical barrier in skin with high melanin concentration, resulting in a “diagnostic blindness” that compromises both healthcare assistance and justice(4). Thus, in this epidemiological scenario, the system’s response becomes compromised. When a physician fails to identify an injury during emergency care or a medico-legal examination, the official document falsely records an “absence of injuries.” This documentary silence generates underreporting of the severity of violence suffered by the Black population and impacts judicial decisions, perpetuating the cycle of impunity. In response to this limitation, international forensic guidelines have advocated the use of Alternate Light Sources (ALS) as a screening tool. This technology allows the emission of specific wavelengths which, associated with barrier filters, can increase the contrast between pigmented skin and extravasated hemoglobin, making injuries hidden under common light visible(4). The present study is based on a critical analysis of the literature with the objective of presenting a technical proposal for the implementation of Alternate Light Sources (ALS) as a forensic screening protocol in Brazil. It seeks to substantiate the need to overcome visual inspection exclusively under white light, mitigating “diagnostic blindness” in Black individuals.
2. MATERIAL AND METHOD
This theoretical-doctrinal study is based on a critical analysis of the literature with the aim of presenting a technical proposal for the implementation of Alternative Light Sources (ALS) as a forensic screening protocol in Brazil.
3.DISCUSSION
3.1 BRIEF THEORETICAL FOUNDATION OF ALS
Forensics plays the role of establishing the causal link between the traces found and the crime under investigation. To this end, the physical examination of violence victims is an essential part of the medical evaluation and requires that injuries be described, measured, and documented. One of the most frequently sought injuries in blunt trauma is ecchymosis(4,5). For an ecchymosis to be visible under white light, the examiner must be able to observe the extravasated hemoglobin (or its byproducts) in the dermis (where blood vessels are located). Thus, light must strike the epidermis, penetrate to the dermis, encounter the blood interspersed there, and be reflected back to the observer’s eyes(4,6,7). Furthermore, there must be contrast between the injured area and the surrounding area, for if both possess the same coloration, it will not be possible to distinguish between them. In more pigmented skin, clinical observation under white light encounters a critical biophysical limitation. Melanin, produced by melanocytes in the epidermis, acts as an efficient filter, absorbing a large part of the light before it reaches the extravasated hemoglobin(4,6,7). The result is that the reflection of light back to the observer’s eyes is dramatically reduced, making the present ecchymosis obscured or even invisible. The effectiveness of visual detection, therefore, is inversely proportional to the concentration of melanin in the skin, leading to false-negative diagnoses, in addition to hindering the determination of the injury mechanism. This is a methodological bias exacerbated by the lack of specific training for professionals in the use of appropriate tools(3,4,6,7). The technical response to this barrier is based on the application of cutaneous optical fluorescence. According to Stokes’ Shift, when specific wavelengths of the electromagnetic spectrum are incident upon the skin, instead of white light, energy is absorbed by the tissues and re-emitted at a longer wavelength (lower energy), increasing the contrast between the skin and the affected site(3,7,8). To observe this phenomenon, it is necessary to separate the incident light (excitation wavelength) from the reflected light (longer wavelength and lower energy), which is done through barrier filters. These filters function to block the excitation light (emitted by the ALS) while simultaneously allowing only the fluorescence emitted by human skin to pass through(3,7,8). Spectrophotometric analysis demonstrates that oxyhemoglobin has an absorption peak (Soret Band) at 415nm, which shifts to 430nm (Red Shift) in deoxyhemoglobin and to 460nm in bilirubin(7,8). Therefore, ecchymoses illuminated by ALS with wavelengths near these revealed greater detail, contrast, and extent compared to their appearance under white light(7).
3.2 ALS – SCREENING TOOL
Although there are methodological questions regarding the absolute diagnostic accuracy of the tool — such as the critique by Hauda et al.(9) against its isolated use to detect clinically occult ecchymoses —, the statistical robustness presented in response by Downing et al.(10) is undeniable for screening purposes. By analyzing more than 31,000 observations while controlling for confounding factors, the authors demonstrated that the use of 415nm and 450nm combined with yellow or orange filters significantly increases the probability of ecchymosis detection, potentially reaching up to 5 times (odds ratio: 5.34, 95% CI [4.35, 6.56], p < 0.0001) compared to white light(3,9,10). Numerous other studies over more than twenty years have contributed to these assertions(4). In this doctrinal context, ALS should not be understood as isolated and irrefutable evidence, but rather as a screening tool. Scientific criticism serves to reinforce caution: ALS illuminates the clue, functioning as a high-sensitivity filter to prevent real injuries from going unnoticed (false negatives), ensuring that forensics is not blind to the violence suffered by Black people(11). Analogously, ALS are already widely employed in Criminalistics as a screening tool at crime scenes for the initial identification of latent biological traces, accepting the possibility of false-positives generated by everyday substances (such as detergents, cosmetics, and bleaches)(11,12). Thus, it would not be scientifically acceptable to require that the use of ALS be free of interference exclusively when applied to the detection of ecchymoses. Such a requirement for isolated diagnostic perfection disregards the complementary nature of this forensic examination and, in practice, imposes a technical barrier that perpetuates the risk to racial equity(11,12). In this direction, it is possible to apply the use of alternate light as a component of a complete medico-legal examination, which naturally includes anamnesis and physical examination, and requires the adoption of specific care. Anderson et al. (12) summarized this necessity well:
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History Taking: Ask the patient if they have applied any cosmetic products to the trauma areas since their last bath.
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Evidence Collection: Swab the area positive for evidence of traces.
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Cleaning: Gentle cleaning is recommended (soap and water, alcohol wipes, or makeup remover wipes — which exhibited similar efficacy in removing cosmetics).
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Examine and Photograph: Document any areas with positive findings (fluorescence or absorption) through photography and body mapping. The application of forensic light should occur using 415nm or 450nm wavelengths with yellow or orange barrier filters. The application site should be as dark as possible. The use of ALS as a screening tool, when adapted to the Brazilian reality and its need for answers to legal interrogatories (quesitos), would allow the expert, in the event of positive fluorescence in Black individuals, to at least declare a lack of elements to affirm or deny the existence of bodily offense caused by a blunt agent. Conversely, in the case of no fluorescence, it contributes to confirming that there are no traces of bodily offense—visible superficial ecchymosis at that moment in the observed region (given its high sensitivity).
4. PRACTICAL LIMITATIONS OF THE METHOD
Based on differences in light absorption by hemoglobin and its byproducts, it was believed for some time that ALS could fill the void in ecchymosis dating left by the failure of Le Grand du Saulle’s ecchymotic spectrum to survive evidence-based medicine(13). However, studies have shown that ALS is also unreliable for dating ecchymoses(14,15). Positive results should not be viewed as pathognomonic for ecchymosis, but rather as consistent with reports of blunt trauma in a specific region by the victim(12). This is due to the risk of fluorescence from cosmetics, scars, abrasions, excessive freckles, or even hemangiomas (in cadavers)(3, 12, 15, 16).
5. CONCLUSION
The limitation of white light inaugurates a “chain of invisibility.” If the injury is not seen during initial care, the forensic report/medical record falsely registers an “absence of injuries”; this error contaminates the entire criminal prosecution and results in underreporting. This analysis substantiates that traditional visual inspection in Black individuals is technically and ethically insufficient. The incorporation of ALS should not be seen merely as a technological acquisition, but as a strategy for guaranteeing rights. There is an urgent need to create national protocols that validate and standardize the use of ALS (415nm/450nm with yellow/orange filters) as a mandatory screening step for Black victims. Such a measure is indispensable to mitigate racial diagnostic bias, qualify epidemiological data on violence and, above all, fulfill the constitutional principle of equity in the Brazilian medico-legal system.
References
1. Instituto Brasileiro de Geografia e Estatística (IBGE). Censo Demográfico 2022: Identificação étnico-racial da população, por sexo e idade: Resultados do universo. Rio de Janeiro: IBGE; 2023. [citado em 2025 Nov 19]. Disponível em: https://biblioteca.ibge.gov.br/index.php/biblioteca-catalogo?view=detalhes&id=73105.
2. Instituto de Pesquisa Econômica Aplicada (IPEA); Fórum Brasileiro de Segurança Pública (FBSP). Atlas da Violência 2023. São Paulo: FBSP/IPEA; 2023. [citado em 2025 Nov 19]. Disponível em: https://www.ipea.gov.br/portal/relatorios
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