Mobile phone simulating call to German Chancellor Merkel next to a tablet showing the logo of NSA is seen in picture illustration taken in FrankfurtA federal appeals court in the District of Columbia heard oral arguments Tuesday over the constitutionality of the National Security Agency’s mass collection of data about millions of Americans’ phone calls. The three-judge panel wrestled with key questions, including at what point a person’s privacy rights become relevant — when the government gathers records known as metadata or when an analyst reviews the material. They pressed attorneys on whether a 1979 Supreme Court case about privacy rights in phone-call data applies to the NSA program. More