Who Is Watching the Watchers?

"The program has touched many more Americans than that. Surveillance takes place in several stages, officials said, the earliest by machine. Computer-controlled systems collect and sift basic information about hundreds of thousands of faxes, e-mails and telephone calls into and out of the United States before selecting the ones for scrutiny by human eyes and ears.

Successive stages of filtering grow more intrusive as artificial intelligence systems rank voice and data traffic in order of likeliest interest to human analysts. But intelligence officers, who test the computer judgments by listening initially to brief fragments of conversation, 'wash out' most of the leads within days or weeks.

The scale of warrantless surveillance, and the high proportion of bystanders swept in, sheds new light on Bush's circumvention of the courts. National security lawyers, in and out of government, said the washout rate raised fresh doubts about the program's lawfulness under the Fourth Amendment, because a search cannot be judged 'reasonable' if it is based on evidence that experience shows to be unreliable. Other officials said the disclosures might shift the terms of public debate, altering perceptions about the balance between privacy lost and security gained."

Surveillance Net Yields Few Suspects