With up to 320,000 service members sustaining some form of traumatic brain injury TBI over the past 14 years, the lack of an objective measurement tool for evaluation and monitoring of TBI is of great concern to the military. The NeuroCom Sensory Organization Test SOT is the current gold standard for assessing mTBI-related motor impairments. However, the equipments size and logistical footprint makes it impractical for field deployment. This study seeks to determine the validity and reliability of an Android device-based mTBI mild traumatic brain injury screening test app for assessing motor function. The app, AccWalker, utilizes the smartphones accelerometer and orientation metrics in order to assess a persons functional motor ability. The study will seek to establish test-retest and inter-rater reliability of the app within a healthy civilian population, concurrent validity with the SOT, BESS, CB and M test three currently used assessments in a healthy civilian population, and predictive validity to discriminate between healthy individuals and those with clinically confirmed mTBI in both a civilian and military population.