Quantification of luminol chemiluminescence: a tool for estimating the postmortem interval of skeletal human remains

Postmortem interval (PMI) estimation is mandatory in any forensic investigation. Although it remains a very challenging task, particularly in skeletonized human remains. Luminol chemiluminescence has been explored as a tool for PMI estimation, however, its application requires further experimental validation to ensure accuracy and reproducibility. The present research aims to increase the objectivity of PMI estimation by quantifying the light emission from the luminol chemiluminescence reaction. For this purpose, a sample of clavicles collected from 24 adult individuals of both sexes, with known PMI ranging from 7 to approximately 500 years, was selected. After being reduced to powder, the samples were analyzed on a CCD camera with an image intensifier, and the reaction Ipeak was measured. The results obtained revealed a clear inverse relationship between PMI and Ipeak values. A segmented regression analysis identified a statistically supported threshold at approximately 30 years postmortem, distinguishing a variable early postmortem phase from a long-term phase characterized by consistently low and minimally variable chemiluminescence intensities. This pilot study supports the validity of quantifying the luminol chemiluminescence reaction as a feasible and informative presumptive screening tool for PMI estimation, with potential applicability in distinguishing remains of forensic interest from those of archaeological relevance.