This thesis would not have been possible without the support and guidance of many people. First, I would like to express my deepest gratitude to my advisor, Dr. Arun Ross. I vividly remember my initial interactions with him during the first semester of my Masters, when he taught the Introduction to Biometrics course. Little did I know that he would greatly inspire me in pursuing both, Masters and PhD in the field of biometrics. His dedication, patience, and hardworking nature have constantly inspired me over the years. Working with him has taught me to conduct research with rigor, and present my work with clarity. I truly consider it as a privilege to have him as an advisor and instructor throughout my graduate studies. I would like to thank my committee members for their valuable guidance and suggestions in my research. Dr. Xin Li's courses in image-and video-processing have been extremely helpful in getting started with my research. My thesis has been greatly benefitted by Dr. Donald Adjeroh's detailed feedback. It was Dr. Lawrence Hornak who inspired me to think practically in research. Special thanks to Dr. Vijayakumar Bhagavatula, who agreed to be a member of my committee on a short notice. His discussions during IARPA meetings and subsequent thesis presentations reminded me to maintain novelty in my work.