When US federal officials recently confirmed the existence of a massive National Security Agency programme that has been collecting Americans' phone data for years, they argued it was needed to fight terrorism.
But that acknowledgment has opened potentially seismic rifts in the nation's legal system, allowing defendants to argue that the government is holding a massive trove of evidence that is necessary to their cases - the kind of evidence that, when it is collected by police, is commonly turned over to defendants.
As a result, one south Florida case has become a surprise focus in the debate over secret government surveillance. It may prompt a mid-trial showdown with the federal government.
Terrance Brown is on trial on suspicion of masterminding a Brinks armoured-truck robbery in south Florida that left a man dead in October 2010. About a week into the trial, The Guardian published a top-secret order showing the US government forced wireless provider Verizon to hand over phone records and metadata on millions of customers daily. Acknowledgment of a broader programme followed.
Phone data has long been used in court to show what defendants were doing - and where they were - at the time of a crime.
In Brown's case, the FBI used phone data to compile maps to show at least one of Brown's co-defendants had made calls in the area where a series of robberies related to the case were committed. Investigators were unable to find all the relevant data for Brown's phones because his carrier apparently did not keep records covering the entire span of the crimes.
On Sunday, after federal officials acknowledged the NSA trove, Brown's lawyer, Marshall Dore Louis, filed a mid-trial motion asking the NSA to turn over Brown's phone records.
"The records are material and favourable to Mr Brown's defence," Louis wrote.
US District Judge Robin Rosenbaum asked the Justice Department to file a response by Wednesday, so she can decide on the request. She added that she would review the legality of any NSA data gathered on Brown.