The mail cover, a decades-old, low-tech investigative tool consisting of recording the information on the outside of mail delivered to a law enforcement target, is thriving. Its use has risen by more than half since the mid-1980s. Defense and civil rights lawyers say they've been largely unaware that mail covers are being conducted -- which is exactly the way the government prefers it.
Mail-Watching Is Alive and Well
The National Law Journal
April 1, 2002