This is a story about what can happen when no one is looking. For the patients at Universal Pain Management, a medical clinic in northern Los Angeles County, Dr. Francis Riegler is always looking.

Riegler huddles with the clinic's nurse practitioner over a computer printout. The one-page report from the state's drug-tracking system shows that a patient was on the hunt for more Vicodin, a powerful pain reliever that he was already getting from Riegler's clinic.

California has the oldest continuous prescription-drug monitoring program in the U.S., dating to 1939. It used to rely on carbon copies: one for the pharmacy, one for the doctor and one to be sent to the state's Department of Justice.