EAST German dissidents probably didn’t spot the plain-clothes agent with the
vibrating armpit. But agents could track suspected political opponents without
even seeing them. They just followed a trail of radioactivity shed by their
unwitting quarry.
In the 1970s and 1980s, the German Democratic Republic’s secret
police—the Stasi—frequently labelled suspected dissidents with
highly radioactive chemicals so that agents wearing concealed Geiger counters
could keep tabs on them, according to a paper by Klaus Becker, a leading
radiation protection expert.
So that targets would not hear the clicking of the counter at close range,
Stasi agents wore the detector…
