Detecting a concealed weapon or threat is not easy, even for experienced police officers. Terrorist attacks and bombings at concerts, sporting events and airports underscore the need for accurate and reliable threat detection. However, the likelihood of a police officer identifying someone concealing a gun or bomb is only slightly better than chance, according to new research. Source 5n.
While detecting a concealed weapon is not a easy task to do many of those who are not used to carrying a concealed weapon or other item that they should not have do at times make it easy. If you watch people and are trained to watch people a person who is carrying a concealed weapon will always give themselves away. The less they are used to carrying a concealed weapon the sooner it is apparent.
I will not state how to detect or how it is apparent as that is something that the general public and those who are wanting to do harm to the general public does not need to know.
Yup, there are certain tells that I see this article doesn't take into account. Those trained to do this are quite proficient at it and the science was really advanced by leaps and bounds by the Israelis. As one can imagine, they have an immediate and ongoing concern about this type of activity.