April 26, 2004

A false positive experience

I was returning home from California last Saturday, and I had the early morning flight back from SFO. I tend to get to the airport early, and I arrived at the airport at 5:15 a.m. for my 6:30 a.m. flight. Just as I was thinking that I really need to stop coming so early, I arrived at the security line to find that it was quite short. I did the usual dance of removing my laptop, taking off my shoes, putting my cell phone and wireless email device in a tray, and going through the metal detector. As has happened on a few previous occasions, I was asked if they could take my suitcase to check it. They ran a cloth over the zippers and stuck it in a machine.

To my surprise, a red screen started flashing EXPLOSIVES FOUND, on and off.

I believe that I was more curious than nervous about what would happen next. The security guard asked me in a serious voice to step aside, and started waving for another security person. Two of them hurried over. One of them started asking me some questions, and another started giving the original one instructions. They took all of my luggage, the suitcase and the laptop case, and ran the cloth test on it all, after disinfecting the table and their hands with a solution. Meanwhile, I watched. The most senior looking security guard started reading from what I would call a recipe of instructions. They followed them step by step. Everything they tried turned up negative. They then packed it all up for me and asked me a few questions. What surprised me were the questions they didn't ask. Who else touched my suitcase? Have I had it with me the whole time? Did I pack it? They didn't ask these. In hindsight, I think they were just trying to determine if I was nervous, and if I would be evasive. I was neither.

They asked me if I was on any medication. I happen to be taking something these days, so I said yes. They then asked me if I had just taken any pills recently, and I said yes. They explained to me that sometimes the medication residue on fingers can trigger the machine to think that there are explosives. They thanked me for my patience and let me go.

It was interesting to watch a security system at work. I didn't find any glaring flaws in the way things were handled. The only thing that I didn't like was that they wrote down a lot of stuff, including my drivers license number, my flight information, and my name, and it was all logged. Presumably, my name is now in a database somewhere, and I'm categorized as being a hair more suspicious than other people. I don't like that, but I suppose there is nothing I can do about it.

Posted by Avi Rubin at April 26, 2004 05:00 PM