Re: Second Amendment
They would swab the keyboard and other areas for traces of explosives.
In my experience that still happens from time to time at European airports, happened to me a couple of months ago. I've had my shoes trigger detectors just because I'd walked down a street where a car bomb had gone off several weeks before.
Many years ago a friend told me that his brother had been stopped at airport security. Some detector went beep, and they then scanned all his hand luggage. They wouldn't tell him why at first, but after every item seemed to trigger the detector he was taken aside for an interview and asked "have you been in contact with explosives?". At that point he produced his reservist ID and explained that he was on his way home after having spent a week on a 'handling explosives' course...
At least it shows that the detectors work.