How the Times analyzed records

Here is how The Times matched doctors to their patients who died of prescription drug overdoses or related causes:

Reporters examined coroners’ records in Los Angeles, Orange, San Diego and Ventura counties and identified cases in which:

Toxicology tests found a prescription drug in the deceased’s system, usually a painkiller, anti-anxiety drug or other narcotic.

Coroners’ investigators reported finding a container of the same medication bearing the doctor’s name, or records of a prescription.

The coroner determined that the drug caused or contributed to the death.

The Times gained access to coroners’ files in the four counties through the California Public Records Act. Coroners do not have a uniform category for prescription drug deaths. To identify such cases, reporters inspected electronic and paper records on thousands of drug fatalities.

The Times found 3,733 deaths involving prescription medications from 2006 through 2011. In 1,762 of those cases — 47% — one or more drugs prescribed for the deceased caused or contributed to the death. In a few cases, prescriptions were written by physician assistants or nurse practitioners with a doctor’s authorization.

Most of the deaths were from overdoses. Cases of suffocation or drowning caused by an overdose are also included. Suicides, traffic accidents and other trauma-related deaths involving drugs were excluded.

Also excluded were cases in which the coroner noted that the deceased overdosed on drugs prescribed for someone else.

Riverside, San Bernardino and Santa Barbara counties were not included in the analysis because records were incomplete.