Asking the N.S.A. the Right Question

On March 5, 1976, a Baltimore man named Michael Lee Smith robbed a woman named Patricia McDonough. Smith drove off in a late-model Monte Carlo, which McDonough described to the police. After the robbery, he began making threatening phone calls to his victim. The cops tracked down Smith’s home address by tracing his license-plate number, and they soon set out to prove that he was the same person harassing McDonough over the phone. Without obtaining a court order or warrant, Baltimore police ins...