in finding terrorist suspects. Just as people with the same names as potential suspects are showing up on watchlists, this is not a good way to determine their threat level. While there certainly are many challenges to generating profiles of potential terrorists, this study released by the Proceedings of the National Academies of Science does a mathematical analysis how we’re deploying the profiles we do have, and suggests we may not be using them wisely.
The study was performed by William Press, who does bioinformatics research at the University of Texas, Austin, with a joint appointment at Los Alamos National Labs. His background in statistics is apparent in his ability to handle various mathematical formulae with aplomb, but he’s apparently used to explaining his work to biologists, since the descriptions that surround those formulae make the general outlines of the paper fairly accessible.
Press starts by examining what could be viewed as an idealized situation, at least from the screening perspective: a single perpetrator living under an authoritarian government that has perfect records on its citizens. Applying a profile to those records should allow the government to rank those citizens in order of risk, and it can screen them one-by-one until it identifies the actual perpetrator. Those circumstances lead to a pretty rapid screening process, and they can be generalized out to a situation where there are multiple likely perpetrators.
Things go rapidly sour for this system, however, as soon as you have an imperfect profile. In that case, which is more likely to reflect reality, there’s a finite chance that the screening process misses a likely security risk. Since it works its way through the list of individuals iteratively, it never goes back to rescreen someone that’s made it through the first pass. The impact of this flaw grows rapidly as the ability to accurately match the profile to the data available on an individual gets worse. Since we’ve already said that making a profile is challenging, and we know that even authoritarian governments don’t have perfect information on their citizens, this system is probably worse than random screening in the real world.
Many say racial profiling is just another form of racism, but is it an effect of the TSA in picking out possible suspects, or a reflection on what our society sees as a threat? Either way, just as our not being able to take a big bottle of shampoo on a plane, it’s not making us any safer.