Positive identification using frontal sinus comparisons: Developing empirically-based guidelines

Owing to its unique structure, the frontal sinus is used by medicolegal practitioners to identify unknown decedents by matching antemortem and postmortem radiographs and/or CT scans. While simple visual inspection is often used, this method has been considered too subjective. While several methods based on outline-tracings, linear distances, and coding systems have been developed to objectively assess the sinus for identification purposes, they have not been thoroughly validated and there is no consensus on the most appropriate method. Unanswered questions remain, such as the effects of orientation on sinus identifications and how much sinus variables may change over the course of a few years. The current study will utilize traditional radiographs and CT data to test eight methods for frontal sinus identifications: two outlining methods, two coding/metric methods, two methods of defining sinus absence/presence, and two procedures of visual assessment. Success rates for each method will be based on percent-matches for ante- and post-mortem images. For each method, this study also assesses the following: 1) accuracy & error rates as related to positive identifications; 2) applicability to both traditional radiographs and CT scans, with proposed modifications when changing image modality; 3) intra- & inter-observer reliability; 4) the effect of cranial orientation; 5) the effect of frontal sinus size; and 6) the effect of age-related changes. Compared to previous studies, the current study utilizes larger samples, more varied methods, and several imaging modalities, across which questions about accuracy, inter-/intra-reliability, effects of orientation, effects of sinus size, and effects of age will be empirically addressed. A set of empirically-based guidelines for frontal sinus identification will be developed based on the results, indicating the advantages and limitations of each of the methods, and recommended parameters and applications. Practitioners will be able to refer to these guidelines when making frontal sinus identifications or testifying to them in court. The results of this project will provide clear accuracy and error rates for the various methods, important to meet Daubert guidelines. They will also provide important knowledge regarding potential age-related changes to sinus morphology, effects of orientation, and ability to use the methods interchangeably between radiographs and CT scans. It is important to better understand these variables and method limitations, given the major implications of misidentifying a decedent or erroneously excluding a true identification. Dissemination of results will entail at least five peer-reviewed, presentations at national conferences, and NIJ reports. Note: This project contains a research and/or development component, as defined in applicable law, and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14). CA/NCF