A barrier and system for the protection of a crowd from terrorists, by evaluating each individual for any concealed prohibited items. Each individual is exposed to one or more screening mechanisms, controlled by a monitoring unit, while passing in an organized fashion through an enclosed walkway containing the screening mechanism, and exiting on the other side. When a prohibited object is detected, response is provided and the smart door device is locked to detain and isolate the suspected individual in the device structure's interior. The structure of the invention is also configured to deflect the blast created by a potential explosion and prevent harm to other individuals and structures nearby.