When deploying technology that has the potential to put actual human beings behind bars, what should be the acceptable margin of error? Most human beings, especially those who haven't committed any crime due to their natural aversion to being housed with actual criminals, would prefer (as if they had a choice) this number to be as close to zero as humanly (and technologically) possible.

The FBI, on the other hand, which possesses the technology and power to nudge people towards years of imprisonment, apparently feels a one-in-five chance of bagging the wrong man (or woman) is no reason to hold off on the implementation of facial recognition software.  ...