Another placeholder post for something where I need to get my facts straight, but it's an example that has been rattling around in my head for a couple of years. So the plague hits Glasgow, and in order to save a big chunk of people, the mayor, or somebody, decides to take all the sick people and chuck them in the Catacombs below the city, and then throw away the key.
Lots of potential for both kinds of false positives. See the "quarantine" post. People who are actually not sick can be chucked in the catacombs, and sure enough, if they weren't sick when they were chucked in, after a few hours with genuine plague victims, they'll have it too! A deliberate false positive would be grabbing Noam Chomsky or somebody in the dead of night and chucking him in the catacombs too. It goes both ways - could be that the leftists control the city and they chuck Rush Limbaugh in the catacombs or something. And after a few hours in the company of genuine plague victims, damned if both those guys aren't sick too. That's if it's done for political reasons. An accidental false positive is just, the cops in charge of discerning who to render and who not to render are incompetent and make mistakes. Say 75% of a neighborhood is sick and it's too difficult to try to pick apart who isn't sick, so you take the whole neighborhood.
Because you, the policeman, would catch a lot more flak for being insufficiently thorough than you will for being a little over-thorough.
Hat tip to the lovely Rosie Weber of London town for suggesting the Glasgow story while hanging out at a cafe in North Beach.
Grim ideas, but it's kind of empowering and fun to have this stuff all in one place. The posts have been pouring out of me.