Abstract: Embodiments relate to appearance model based automatic detection in sensor images. In one arrangement, a detection apparatus of an Automated Threat Detection system utilizes generative, statistical models of human appearance in sensor images, such as MMW images, as a basis for comparison with images received by a sensor such as an MMW sensor. The detection apparatus can effectively replicate, through the models, the approach of human observers to provide a relatively high throughput of subjects. Additionally, by utilizing generative, statistical models as the basis for comparison against received MMW images, the detection apparatus can minimize detection errors caused by variance in body geometry, skin reflectance, and posture of the subject to maintain a relatively low rate of false alarms and a relatively high rate of detection of threats.