Statisticians at the University of Texas have demonstrated that using racial profiling to catch terrorists isn't just politically and ethically questionable - it's also not very effective.
Racial profiling is based on the idea that people from particular racial or ethnic groups are more likely to be involved in acts of terror. The idea is that law enforcement officers should focus particularly on people from these 'high risk' groups.
One obvious problem with this approach is that innocent people who also belong to the targeted group rapidly become upset - with some even becoming radicalised as a result. Another is that not every potential terrorist has a long beard and answers to the name Mohammed.
But quite apart from such concerns, says professor William Press, the math of racial targeting simply doesn't add up.
"Racial profiling is as indiscriminate as deciding that people named Patrick are more likely to drink and drive, and so everyone who is named Patrick should be stopped and breathalysed more frequently than people with other names," says Press.
However, using such a strategy can in some ways appear successful. If you keep testing more people named Patrick than other people, you are almost bound to find more Patricks who have drunk alcohol than people with other names. This then leads you to think the problem is even worse than you first suspected - so you start targeting Patricks even more.
In his paper in Significance, Press analyzes the process that underlies racial profiling mathematically, and concludes that many forms of racial profiling result in a smaller chance of detaining a terrorist than carefully conducted standard sampling.
"Uniform sampling, without the use of profiling, is surprisingly good," says Press. "It is robust against false assumptions, it is deterrent, it is easy to implement, it is about as effective as any real-life system can be – and it is devoid of moral and political hazard."