We've been discussing situational awareness and IDing BGs. Here's a piece on a related subject, from the FBI Law Enforcement Bulletin. An excerpt:
"... Sworn law enforcement personnel carry weapons under a multitude of circumstances, not just when in uniform. Other work-related situations can include plainclothes, detective, old-clothes, and tactical assignments. Also, many non duty related circumstances exist in which they may carry weapons. So, how do they act under these and similar circumstances?
Officers who work plainclothes assignments, as well as those who carry handguns off duty, are concerned primarily with firearm concealment, accessibility, and security. Would these matters not be the same for other armed individuals, including criminals? By reflecting on their own behaviors, awareness, and training, as well as refining their powers of observation, officers can enhance their skills in detecting the presence of armed subjects. They should examine not only their own actions but also that of fellow armed officers not in uniform. Do such officers dress in a certain manner that enhances concealment of their firearms? Would offenders do the same? When officers stand, sit, walk, run, or change body positions, do they exhibit specific traits indicating that they possess a firearm? Would armed criminals change body positions similarly? Officers also know that carrying a concealed weapon over an extended period of time may produce certain automatic body movements or gestures, which they may perform without conscious thought. Could offenders who have carried handguns for a long time also display such unconscious actions? ..."
The whole thing is here: