He currently practices as a physician in Northeast Florida and has served as Medical Director for several emergency departments throughout his career. Dr. Marshall has also been a Physician to special mission units and an affiliate faculty member at Johns Hopkins University. His background spans law enforcement, EMS, and academia, with a history of coordinating multi-agency operations and training first responders. He has been involved in high-profile events like the United Nations General Assembly and various national security events. His academic interests include first responder training, wellness, diet, longevity, and rehabilitation. Dr. Marshall holds board certifications in emergency medicine and is recognized for his contributions to government agency medical support and medical planning.