[USA] Detecting Concealed Weapons: Directions for the Future
http://www.ojp.usdoj.gov/nij/journals/258/detecting-concealed-weapons.html
Chris Tillery
"On July 24, 1998, a man entered the US Capitol building in Washington, DC, with a .38-calibre handgun concealed under his clothing. A security check point with a portal weapons-detection system had been established at the entrance of the building. Knowing that his gun would be detected if he walked through the portal, the man stepped around it. Immediately, he was confronted by Jacob Chestnut, one of the Capitol Police officers operating the portal. The man drew his gun and killed Chestnut. He then shot and killed a second officer, John Gibson, before he was stopped. [...] This incident showed the limitations of current security-detection portal systems: they must be near an individual to work. They generally provide sufficient warning when it comes to detecting a knife, but they cannot detect weapons that can kill beyond arm’s reach. By the time a handgun or a bomb vest is detected, it generally is too close to be dealt with safely. But there are ways to provide more warning."