" However—and this is especially troubling—“if analysts stumble across evidence that an American has committed any crime, they will send it to the Justice Department,” the Times wrote. So information that was collected without a warrant—or indeed any involvement by a court at all—for foreign intelligence purposes with little to no privacy protections, can be accessed raw and unfiltered by domestic law enforcement agencies to prosecute Americans with no involvement in threats to national security. "

That is not "spread further". Given the lack of a warrant and probable cause to initiate the search, prosecution using 'serendipitous evidence' flat out contradicts the 4th amendment.