Postmortem fingerprint identification: A novel adaptive approach to the transillumination technique using moistened black volcano powder for fragile epidermal tissue

Abstract

Postmortem identification through fingerprints often encounters significant challenges, particularly with damaged epidermal tissue, due to factors such as carbonization, putrefaction, mummification, or saponification. Traditional techniques frequently fall short in cases involving fragile skin, which complicates the collection of clear fingerprint impressions. This study presents and evaluates an adaptive modification of the transillumination technique, integrating it with moistened black volcano powder to enhance fingerprint recovery from compromised postmortem tissue. A retrospective comparative analysis was conducted on 55 cases processed at the Ricardo Gumbleton Daunt Institute of Identification, São Paulo, Brazil, from January 2012 to May 2022. Of these, 12 cases with both pre- and post-treatment records were selected, totaling 28 distal phalanx samples. The proposed technique involved applying moistened black volcano powder to the epidermis, followed by transillumination and direct photography. The enhanced technique demonstrated a significant improvement in fingerprint quality. Qualitative analysis revealed that all samples treated with moistened black volcano powder clearly presented visible ridges and minutiae, whereas four samples treated with traditional transillumination alone were insufficient for minutia marking. Quantitative analysis indicated that 75% of the samples scored +2 (greater minutiae details and contrast), with an additional 25% scoring +1 (slightly better minutiae details and contrast). The combined use of transillumination and moistened black volcano powder significantly improves the visualization of postmortem fingerprints, providing a reliable method for forensic identification in cases with fragile or compromised epidermal tissue from putrefied or carbonized skin. This technique generates high-resolution fingerprint images that are suitable for database comparison and forensic analysis.

Keywords: compromised friction ridge skin; forensic identification; moistened fingerprint powder; postmortem fingerprint collection; postmortem friction ridge skin enhancement; transillumination technique.