For the last few years, federal agencies have defended body scanning by insisting that all images will be discarded as soon as they're viewed. The Transportation Security Administration claimed last summer, for instance, that "scanned images cannot be stored or recorded."

Now it turns out that some police agencies are storing the controversial images after all. The U.S. Marshals Service admitted this week that it had surreptitiously saved tens of thousands of images recorded with a millimeter wave system at the security checkpoint of a single Florida courthouse.

This follows an earlier disclosure (PDF) by the TSA that it requires all airport body scanners it purchases to be able to store and transmit images for "testing, training, and evaluation purposes." The agency says, however, that those capabilities are not normally activated when the devices are installed at airports.