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An Assessment of Intra- and Interobserver Error in Luminol Chemiluminescence as a Presumptive Test for Postmortem Interval Estimation

Publication . Ermida, Catarina; Rosa, Joana; Cunha, Eugénia; Ferreira, Maria Teresa

Postmortem interval (PMI) estimation constitutes a challenge for forensic anthropologists.The application of the luminol technique as a preliminary test for PMI estimation is considered easy to use and inexpensive. The objective of our study is to validate luminol chemiluminescence testing through the assessment of intra- and interobserver error. Our sample included 266 human clavicles, with known PMIs ranging between 2655 days and 450 years. After sample preparation, luminol was applied, and the results were observed by two different observers. The intensity of the reaction was measured using a binary scale and a 5-level scale, according to the increasing degree of chemiluminescence. The Kappa statistic was used for the assessment of the intra- and interobserver agreement. The obtained results showed total interobserver error agreement regarding the binary scale and a K = 0.98 (95% CI: 0.97–0.99) regarding the 5-level scale. Additionally, Observer 1 and Observer 2 obtained a 100% agreement concerning the binary scale and a K = 1 (95%CI 0.99–1) and K = 0.99 (95% CI 0.99–1), respectively, concerning the 5-level scale. According to our research, it is possible to conclude that luminol chemiluminescence testing is suitable as a rapid diagnostic test, revealing this method as practically independent of observation error

2023Journal article

Open access

Luminol and the postmortem interval estimation — influence of taphonomic factors

Publication . Ermida, Catarina; Cunha, Eugénia; Ferreira, Maria Teresa

The estimation of the postmortem interval (PMI) is one of the key challenges for forensic anthropologists. Although there are several methods referenced for this purpose, none is sufficiently effective. One of the main reasons justifying the complexity of this task is the influence of several taphonomic factors.The study of the Luminol technique has stood out as a promising method for estimating PMI, complementing the existing methods, since it is an economic, easy and reproducible method that operates as a presumptive test. However, it is not known which taphonomic factors can influence the results obtained by this technique.The aim of this study is to test the influence of taphonomic factors, such as temperature, humidity, soil type and pH, on the estimation of the PMI by the Luminol technique.In order to test the influence of the referred factors, a sample consisting of 30 clavicles, with known and similar PMI, collected from autopsies, was distributed as evenly as possible by six vases and buried with different decomposition conditions for a period of 12 months. After the exhumation and sample preparation, the Luminol technique was applied.It was possible to clearly observe differences in the results. Thus, according to our research, it is possible to conclude that the results obtained by the application of Luminol are influenced by taphonomic factors. Therefore, the context in which a body is found should always be considered for applying this technique.

2024Journal article

Open access

Postmortem interval estimation of human skeletonized remains through luminol chemiluminescence

Publication . Ermida, Catarina; Rosa, Joana; Cunha, Eugénia; Ferreira, Maria Teresa

Postmortem interval (PMI) estimation represents a significant challenge in the forensic sciences, particularly when dealing with human skeletal remains. A screening protocol for distinguishing possible remains of forensic interest is a crucial tool for judicial purposes. In this context, luminol chemiluminescence emerges as a promising method, with low overall costs and required time. This method is primarily used as a presumptive test, based on the understanding that the intensity of the chemiluminescence reactions decreases with an increase in the postmortem interval, thus underlining its practical implications. This research aims to expand previous research on the potential of luminol chemiluminescence, evaluating its usefulness in estimating PMI. Our sample comprised 239 human clavicles, with known PMI. The luminol solution was sprayed on each powder bone sample in a dark room, observed by the naked eye and photographed. The intensity of the chemiluminescence reaction was measured using a binary and a 5-level scale. The present results reveal that this method is a suitable tool for PMI estimation as a presumptive test, reducing time and costs in criminal investigations. The findings underscore the high sensitivity of luminol chemiluminescence for detecting recent PMI but also highlight a notable incidence of false positives. Thus, our results confirm luminol chemiluminescence as a powerful tool for dating time of death, particularly for identifying forensic relevant remains. Still, the relatively low specificity indicates that it should be complemented with additional tests for further confirmation and scientific validation of the remains’ forensic relevance.

2024Journal article

Open access