The Dog That Didn't Bark

Silver Blaze is one of the most popular Sherlock Holmes stories, in part because (spoiler alert for a 118-year old story you can read by clicking that first link) the mystery is in part solved by Holmes recognizing that something didn’t happen:

“Is there any point to which you would wish to draw my attention?”

“To the curious incident of the dog in the night-time.”

“The dog did nothing in the night-time.”

“That was the curious incident,” remarked Sherlock Holmes.

Holmes realizes the guard dog didn’t bark because it knew the perpetrator of the crime. The absence of an expected happenstance is a signal.

This is what I was getting at when I was writing about spreadsheet errors being a signal that institutions are more robust than they initially appear. The spreadsheets they depend on have a surprisingly high error rate, but these errors are only rarely transmitted to their public behavior.

This was on my mind again this week because of the outcry over the Transportation Security Administration’s new screening measures that take nearly-naked photos of passengers or, for those who opt out, an invasive pat-down. The TSA claims that this policy strikes a balance between privacy and security, and that “We have to ensure that each person getting on every flight is secure.”

Which is not really news. The TSA justifies everything they do by saying it’s “for security purposes” like a magician says “abracadabra”. Words are uttered but no meaning is produced, the speaker is filling time while they do whatever they like.

When you look at those security purposes, the dog isn’t barking. There are no attacks on “soft targets” where people congregate like malls, churches, sporting events, and airport security lines. If the terrorists existed, why don’t they attack?

Carl Sagan pointed out pointed out that “absence of evidence is not evidence of absence”, but he said it because he was dealing with cranks who tried to shift the burden of proof to scientists to disprove their weird theories about flying saucers instead of proving that they exist. Where’s the burden of proof for these searches?

No one disputes that terrorists do exist, the question is whether they’re adequately addressed by existing law enforcement or if the government has reason to employ low-trained workers to grope 3 year olds. U.S. law does not default to requiring everyone to submit to searches, it requires that law enforcement prove in warrants or articulable facts why each search is needed by the particular circumstances. Blanket searches are permitted to enforce immigration and import law, but searches of the person of every domestic airline passenger are far removed from that need.

In short, the TSA hasn’t made a case for these searches, let alone proved it or gotten judicial approval, and the curious incident of the terrorist in the strip mall is an indication we need to pay attention.