A secretive U.S. Drug Enforcement Administration unit is funneling information from intelligence intercepts, wiretaps, informants and a massive database of telephone records to authorities across the nation to help them launch criminal investigations of Americans.
Although these cases rarely involve national security issues, documents reviewed by Reuters show that law enforcement agents have been directed to conceal how such investigations truly begin - not only from defense lawyers but also sometimes from prosecutors and judges.
The undated documents show that federal agents are trained to "recreate" the investigative trail to effectively cover up where the information originated, a practice that some experts say violates a defendant's Constitutional right to a fair trial. If defendants don't know how an investigation began, they cannot know to ask to review potential sources of exculpatory evidence - information that could reveal entrapment, mistakes or biased witnesses.
For the rest of the story: http://www.reuters.com/article/2013/08/05/us-dea-sod-idUSBRE97409R20130805