This is one of those areas of training that most folks totally neglect but when you do the math on the odds of the average joe citizen becoming illegally detained in the 21st century cancel culture you will quickly see this is an area of training you need to focus on NOW!
BARIUM MEAL: The technique of providing a suspect with a traceable item of information and then watching to monitor its progress in the hope of tracing it to an adversary is known as a barium meal after the medical procedure that allows physicians to follow the passage of mildly radioactive material through the body.
Often used to find “leaks” in the espionage, counter-espionage and organized crime circles, this is where a false piece of attractive intelligence is given to a suspected traitor to see where it “comes out on the other side” This is where the enema saying comes from.
During the Cold War this technique was used quite extensively to see how bad an agency or agent had been penetrated and/or compromised. Very often it was insignificant and small pieces of false “treasure” that gave away traitors, ie small details that might be overlooked in a standard report.