I think what&#x27;s really being alluded to is that regardless of your accuracy (unless it&#x27;s 0% or 100%), your false-positives will always be subject to your inputs.<p>Put another way, if you have <i>no</i> terrorists going through, then your false positive matches will always be greater than or equal to your positive matches, and in this case, equal only when they are both zero, since there would never be a real positive.<p>In a less extreme case, such as the reality we live in, we have many millions of non-terrorists and a few terrorists, and even with three nines of accuracy, it&#x27;s likely your false positive matches far outweigh your real positive matches.