THE PETROUS PORTION OF THE HUMAN TEMPORAL BONE: POTENTIAL FOR FORENSIC INDIVIDUATION A Dissertation by JASON MATTHEW WIERSEMA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2006 Major Subject: Anthropology THE PETROUS PORTION OF THE HUMAN TEMPORAL BONE: POTENTIAL FOR FORENSIC INDIVIDUATION A Dissertation by JASON MATTHEW WIERSEMA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Lori E. Wright Committee Members, Sheela Athreya Darryl de Ruiter Gary McCord Head of Department, David L. Carlson August 2006 Major Subject: Anthropology iii ABSTRACT The Petrous Portion of the Human Temporal Bone: Potential for Forensic Individuation. (August 2006) Jason Matthew Wiersema, B.A., Texas State University; M.A., California State University, Chico Chair of Advisory Committee: Dr. Lori E. Wright In this dissertation I evaluate the potential of the morphology of the petrous portion of the human temporal bone as seen on axial CT scans of the head as a means to generate identifications of fragmentary human skeletal remains. The specific goals are threefold: (1) To investigate variability in the shape of the petrous portion of the human temporal bone using two-dimensional morphometric analysis; (2) to evaluate the reliability of the resultant method in forensic identification; and (3) to consider the results within the framework of Bayesian theory in light of recent rulings regarding the admissibility of forensic testimony. The data used in this research were collected from axial CT images of the cranium. Two sets of images were collected for each of the 115 individuals in the sample so that Euclidean distance comparisons could be made between images of the same individual and images from different individuals. I collected iv two-dimensional coordinate data from 36 landmarks on each of the CT images and calculated the distances between each of the coordinate points to generate the data used in the statistical analyses. I pared down this set of measurements using two different models (referred to as the biological and PCFA models). The measurement sets of both models were then compared to one another using nearest neighbor analysis, to test their relative efficiency in matching replicate images to one another. The results of both models were highly accurate. Three incorrect nearest neighbor matches resulted from the biological model and 5 from the PCFA model. The errors appear to have been the result of variation in the axial plane between the first and second scans. The results of the nearest neighbor comparisons were then considered within the context of Bayes’ Theorem by calculating likelihood ratios and posterior probabilities. The likelihood ratios and posterior probabilities were very high for both models, indicating that: 1) there is significant individual variability in the measurements of the petrous portion used in this research, and 2) this variation represents a high level of potential accuracy in the application of this method in the identification of forensic remains. v ACKNOWLEDGEMENTS I owe a large number of people a great deal of gratitude for their contributions to the success of this dissertation and to my graduate career. The members of my committee, Dr. Lori Wright, Dr. Sheela Athreya, Dr. Darryl de Ruiter and Dr. Gary McCord were obviously instrumental in the completing of this research, but also went far beyond what was required of them in offering assistance and guidance. Dr. Lori Wright deserves particular gratitude for her unwavering confidence and support of my progress. It was often her confidence that convinced me that I could proceed. Dr. David Carlson, the Chair of the Anthropology Department deserves many thanks. He was always eager and available to provide methodological and statistical assistance, and his input is evident throughout this dissertation. Dr. Gil Naul, Chairman of the Department of Radiology at Scott and White Hospital in Temple deserves thanks for providing me with the CT images on which my research was based and for making the process of acquiring those images significantly less complex than it would otherwise have been. David Glassman, my mentor as an undergraduate, whose unique brand of honest advice is still spookily meaningful today, deserves much gratitude. Dr. Turhon Murad also has been the source of significant knowledge and advice over the years, and I thank him for that. I also wish to extend my gratitude to Dr Wei-Jung Chen, Associate Professor at the Texas A&M University Health vi Science Center whose patience, as well as his professional and personal guidance during my employment in his laboratory made the last three years both more efficient and more enjoyable. I would also like to thank Dr. Eric Bartelink for what, once again was the ideal environment in which to be a graduate student and write a dissertation. Again, nothing works like a little friendly competition to motivate me, or maybe it was guilt when he was working and I wasn’t. Either way, it worked, thanks Fartolin. Cassady Yoder deserves thanks for her support during the process as we progressed through various stages of this process at the same time. Geoff Denny, my neighbor and friend, will take a long time to repay for all of his help. I extend my gratitude for his help with excel and SPSS, I’m not sure my computer would have survived without it. I’d also thank him also for the coffee, meals, and all of the various other things he did at just the right time to help me out. To my mom and dad, thanks isn’t enough, your moral support has been crucial during this process, especially when I wasn’t sure I could finish. Oh, and thanks to them for bailing me out of my various monetary crunches over the years. Without their help, I would never have finished. Everyone should be so lucky as to have parents like mine. Thanks to my brother, Jared Wiersema for bragging on me all the time, it was nice to know I had him on my side. I also extend many thanks to Alanna Koos for her steadfast support, and periodic motivational speeches. I didn’t want to listen at the time, but I’m glad I did now. I realize now, when I think of those speeches just how well she knows me. vii TABLE OF CONTENTS Page ABSTRACT ......................................................................................................... iii ACKNOWLEDGEMENTS.....................................................................................v TABLE OF CONTENTS...................................................................................... vii LIST OF FIGURES ...............................................................................................x LIST OF TABLES ............................................................................................... xii CHAPTER I INTRODUCTION ............................................................................1 II BACKGROUND OF FORENSIC IDENTIFICATION .......................7 Federal Guidelines for the Admission of Forensic Evidence ....................................................................9 Methods for Personal Identification of Human Remains..................................................................................12 Techniques for Radiographic Identification From the Skeleton...................................................................13 Problems with the Existing Radiological Methods ..................................................................................16 Non-radiographic Identification Methods.................................19 III BACKGROUND OF COMPUTED TOMOGRAPHY......................27 Capabilities and Limitations of Computed Tomography............................................................................33 Implications for the Present Research ....................................53 viii CHAPTER Page IV ANATOMY, ONTOGENY, AND EVOLUTION OF THE HUMAN TEMPORAL BONE.................................................57 Anatomical Regions of the Adult Human Temporal Bone .......................................................................58 Functional Regions of the Petrous Portion of the Human Temporal Bone.....................................................60 Evolution of the Human Temporal Bone .................................90 V MATERIALS AND MEASUREMENT METHODS .......................115 Materials Analyzed................................................................115 Image Analysis .....................................................................118 Coordinate and Measurement Data Collection .....................119 VI REPEATABILITY AND DATA REDUCTION...............................125 Landmark Precision ..............................................................126 Measurement Repeatability ..................................................128 Measurement Reliability........................................................129 Variation Related to Sex, Age and Length of Time Between Scans............................................................134 Data Reduction .....................................................................141 VII NEAREST NEIGHBOR COMPARISONS, LIKELIHOOD ESTIMATES, AND POSTERIOR PROBABILITIES.........................................................................158 Nearest Neighbor Analysis ...................................................159 Summary Statistics ...............................................................161