Parallel construction is a law enforcement technique used to create a separate, legitimate evidentiary basis for an investigation, primarily to conceal the true, often sensitive, origin of the information. In the U.S., a 2013 Reuters report revealed the DEA's Special Operations Division (SOD) advised agents to employ this tactic for cases derived from NSA warrantless surveillance, essentially "laundering" evidence that might otherwise be inadmissible under the "fruit of the poisonous tree" doctrine. This method allows authorities to protect confidential sources or intelligence methods, for example, by directing agents to a specific location for a "random" drug stop, thus obscuring how initial tips were obtained. The practice gained support following the Supreme Court's 2009 Herring v. United States decision, relating to the good-faith exception for evidence. Beyond modern American drug enforcement, parallel construction was famously used to hide the cracking of the Enigma code during World War II and is also recognized in the UK's Investigatory Powers Act 2016.