The Washington Post reports in a short article on the sometimes strange, sometimes strained relationship between spy agencies like the NSA and CIA and law enforcement (as well as judges and prosecutors) when it comes to evidence gathered using technology or techniques that the spy agencies would rather not disclose at all, never mind explain in detail. They may both be arms of the U.S. government, but the spy agencies and the law enforcers covet different outcomes. From the article: [S]sometimes it's not just the tool that is classified, but the existence itself of the capability — the idea that a certain type of communication can be wiretapped — that is secret. One former senior federal prosecutor said he knew of at least two instances where surveillance tools that the FBI criminal investigators wanted to use "got formally classified in a big hurry" to forestall the risk that the technique would be revealed in a criminal trial. "People on the national security side got incredibly wound up about it," said the former official, who like others interviewed on the issue spoke on condition of anonymity because of the topic’s sensitivity. "The bottom line is: Toys get taken away and put on a very, very high shelf. Only people in the intelligence community can use them." ... The DEA in particular was concerned that if it came up with a capability, the National Security Agency or CIA would rush to classify it, said a former Justice Department official.