Luminol chemiluminescence: contribution to postmortem interval determination of skeletonized remains in Portuguese forensic context

Postmortem interval (PMI) determination is one of the main challenges of forensic anthropology, and there are several referenced methods that consider intrinsic and extrinsic factors to the skeletonized remains. Therefore, there is an important need to develop a precise, economic, easy and reproducible technique, which will operate as a presumptive test. The chemical reaction that occurs in the presence of luminol, chemiluminescence, is used as a work tool to evaluate the PMI. This is given by luminol high affinity for haemoglobin, which is secured in bone tissue by its high mineral content, after the blood supply ceases postmortem. We evaluated a luminol-based technique, in which we measured the chemiluminescence of skeletonized remains as an indicator of the PMI. We assessed the usage of this technique for PMI estimation and for deciding whether remains have forensic interest, particularly in the Portuguese medicolegal context. Additionally, we evaluate the reproducibility of this technique. The test sample consists of 50 skeletonized individuals of both sexes, adults, between 20 and 98 years, with a known time since death and without bone pathologies. The results of Kappa statistic, with values between 0.79 and 0.97, showed high interobserver and intraobserver agreement when applying the luminol test as a presumption test. We concluded that this technique alone is not precise and of limited value to determine forensic relevance in the Portuguese context. However, it can be used as a presumptive test, reducing time and costs in criminal investigation.