Forensic Identification of Decomposed Human Body through Comparison between Ante-Mortem and Post-Mortem CT Images of Frontal Sinuses: Case Report.

OBJECTIVE: The aim of this paper is to report on a case of positive human identification of a decomposed body after the comparison of ante-mortem (AM) and port-mortem (PM) computed tomography images of frontal sinus. CASE REPORT: An unknown, highly decomposed human body, aged between 30 and 40 years, was found in a forest region in Brazil. The dental autopsy revealed several teeth missing AM and the presence of removable partial prostheses. The search for AM data resulted in a sequence of 20 axial images of the paranasal sinuses obtained by Multislice Computed Tomography (MSCT). PM reproduction of the MSCT images was performed in order to enable a comparative identification. After a direct confrontation between AM/PM MSCT, the data were collected for morphological findings, specifically for the lateral expansion of the left lobe, the anteroposterior dimension, and the position of median and accessory septa of the sinuses.
CONCLUSION: The importance of storing and interpreting radiographic medical data properly is highlighted in this text, thus pointing out the importance of application of forensic radiology in the field of law.

Introduction

Forensic radiology as an emerging branch of forensic sciences plays a valuable role by providing answers about deceased individuals in court procedures, particularly those related to the cause of death () and identification of unknown victims (). In general, it provides solid ante mortem (AM) radiographic evidence for comparison with postmortem findings in human identifications () which are registered mainly through conventional dental and maxillofacial radiographs (). However, in the last few years, computed tomography (CT) has become popular in medical routines and has been most frequently used method for providing AM data in the forensic routine (). The present study reports on a case of positive human identification of a heavily decomposed human body. A comparison was made between AM and PM forensic evidence registered from CT images of frontal sinuses.

Case report

In 2013, heavily decomposed human remains were found in a forest region in Brazil. After the crime scene investigation, the remains were referred for forensic exams at the local medico-legal institute. The anthropological analysis pointed to a female victim aged between 30 and 40 years (, ), with height ranging from 158mm to 166mm (). The dental autopsy revealed the presence of removable partial prostheses and several AM missing teeth.

In parallel, Police acknowledged they believed that a 33-year-old woman who went missing for seven days was the victim of a crime. The relatives of the missing person were asked to provide any AM medical or dental records to support the evidence and enable a comparative human identification. The search resulted in a sequence of 20 axial images of the paranasal sinuses obtained by Multislice Computed Tomography (MSCT) dating from 2012 (Figure 1). Three images showed clearly the anteroposterior and lateral dimensions of the frontal sinuses, including its lobes and septa (median and accessory). Complete DICOM files were requested resulting unsuccessfully because no record of the MSCT exam was found archived at the local hospital.

Figure 1

– Axial view of the computed tomography images obtained ante-mortem, dating from 2012

The similarity between the anthropological profile of the victim and the missing person led to the PM preliminary analysis of the frontal sinuses using a posteroanterior radiograph of the skull (Figure 2). Bilateral frontal sinuses of small dimensions were observed, as well as a median septum dislocated to the right side and a left lobe with larger lateral expansion compared to the contralateral. Afterwards, a PM cone-beam computed tomography (CBCT) exam was performed using a CB500 Gendex® (KaVo Kerr Group®, Germany) unit enabling the AM/PM CT data comparison (Figure 3). In Osirix® (Pixmeo Sarl®, Switzerland) DICOM viewer, the PM slices that reproduced the best AM images of the frontal sinuses were searched.

Figure 2

– Radiographic morphology of the frontal sinuses observed in the post-mortem posteroanterior radiograph of the skull, dating from 2013

Figure 3

– Comparison between ante-mortem (AM) and post-mortem (PM) images showing the inferior (A), intermediate (B) and superior (C) regions of the frontal sinuses

The direct comparison between AM/PM CT data was made and morphological findings of the frontal sinuses of the victim were shown to be consistent with those belonging to the missing person. Specifically, the compatibility between data was found on the lateral expansion of the left lobe, the anteroposterior dimension, and the position of median and accessory septa. An evidence-based positive identification of human remains was established.

Discussion

The increasing demand for CT exams in the routine of medical services triggers a modification in the contemporary AM/PM data, which migrates from the conventional radiographs to more technological imaging modalities. The human identification process benefits from this modification achieving more realistic and reliable comparison of forensic data (, ). The use of high-tech imaging techniques plays a valuable role in complex cases involving decomposed/charred bodies and skeletal remains, from which soft tissues and fingerprints are frequently damaged (, ).

The scientific literature supports the findings of the radiographic analysis of the frontal sinus for human identification purposes based on its distinctive morphological pattern () and low prevalence rate for agenesis (). Traditionally, the frontal sinus is assessed with posteroanterior radiographs of the skull (, ) in which the analysis of vertical and horizontal dimensions is performed. The analysis of anteroposterior dimensions remains unfeasible due to the inherent bidimensional (2D) aspect of the technique (, ). Although they were not available in the present case, complete DICOM files from CT scans of the frontal sinuses could enable the analysis of volumetric (3D) dimensions (, ) and improve the interpretation of findings to support a positive identification. Apart from the three-dimensional (3D) analysis, it is important to highlight the recent literature that explores the potential use of the paranasal sinuses registered radiographically (2D) for human identification (). For example, the maxillary sinuses can be measured for sex discrimination to aid reconstructive identifications via forensic anthropology (). Moreover, these pathways for assessing the biological profile of the victims are essential especially in more complex situations, such as incidents involving multiple deaths, due to their potential for narrowing the lists of missing persons.

Another topic of relevance in the present case was the comparison between AM MSCT images and PM CBCT images. Despite being found in some medical services, MSCT units have not become commonly used in a large number of medico-legal facilities worldwide. In the present study, Cone Beam Computed Tomography (CBCT) was the available alternative to enable a similar image analysis and to properly reproduce PM axial images obtained from AM images. So far, there have been no studies in the literature which have reported a case of human identification based exclusively on morphological forensic evidence observed in CT axial images of the frontal sinuses.

Conclusion

The present case report points out that it is very important that the images are stored properly in order to be clinically useful. Also, it highlights the fact that such images need to be provided for court procedures. Additionally, it encourages the training on the interpretation of CT images of the frontal sinus to support cases in which they are the only available forensic evidence.