The mosaic theory of intelligence gathering is a method used by American intelligence analysts. Some legal scholars have been critical of how the application of mosaic theory might undermine civil rights.
As practiced in the CIA's black sites and the US military's interrogation centers at Guantanamo, Bagram Theater Internment Facility, and Kandahar detention facility captives who were not themselves suspected of an involvement with terrorism were nevertheless held, and interrogated, because someone they had an innocent association with was suspected of an involvement with terrorism. Interrogation of these individuals, in great detail, en masse, was believed to allow analysts to fill in the mosaic and the milieu of actual terrorists.
The method was learned by financial analysist Harry Markopolos during his Army Reserve service, and was credited by him as a major tool used in exposing the Bernie Madoff Ponzi scheme.