In early 1981 Community Hospital of the Valley, a small hospital in Perris, in Riverside County, California, began losing an abnormally large number of its oldest patients. They were gravely ill people, and they died violent, convulsive deaths. Between March 30 and April 22, eleven of them died on the nights that Robert Rubane Diaz, a registered nurse who had worked in cardiac care units in hospitals across Los Angeles, San Bernardino and Riverside counties, was on duty. On April 25 a twelfth patient died the same way at San Gorgonio Pass Memorial Hospital in Banning, where Diaz had worked that day. Someone who knew the pattern contacted the coroner's office.
The investigation that followed was long and complicated. Bodies were exhumed and their tissue tested, and autopsies found that some patients had twenty times the normal amount of lidocaine in their bodies. Lidocaine is a drug routinely used in emergency rooms to steady a heart in acute crisis, and in large doses it kills. Ten hospitals in the three counties went back through the charts of dozens of patients. Investigators examined more than two dozen deaths in Riverside and San Bernardino counties and thirty-three more in Los Angeles County, about sixty sudden deaths in all at hospitals where Diaz had worked, before settling on twelve. By May 1981 his home in the Mojave Desert town of Apple Valley had been searched, and lidocaine was found there along with syringes and morphine. He was forty-three.
He was arrested at his Apple Valley home on November 24, 1981, and charged with twelve murders. The trial did not open until March 1984, and Diaz waived a jury, so the case was heard by Riverside County Superior Court Judge John Barnard alone. The prosecution's experts relied on three kinds of evidence for each of the twelve deaths: the concentration of lidocaine in the body tissue at autopsy, signs that the patient had suffered seizures, and the patient's EKG readings. The state painted Diaz as a man who had wanted to be a doctor and resented that he was not, and who pushed patients toward death with overdoses so that he could be seen bringing them back in front of physicians.
Barnard convicted him of all twelve murders and sentenced him to die in the gas chamber. He imposed a separate death sentence for each murder, though he could have limited the number to two, because of the nature of the crimes. Diaz's lawyers had asked for life imprisonment, arguing that by giving up a jury he had saved the county the cost of a trial. The prosecutor, Patrick Magers, said afterward that Diaz "just sat there with a smirk on his face." Barnard ordered him sent straight to death row at San Quentin.
Diaz said he was innocent at trial and for the rest of his life. His challenge to the evidence rested on the toxicology. At least eleven of the twelve patients had been given lidocaine legitimately, in therapeutic doses, as part of their treatment. In 1992 the California Supreme Court upheld the convictions, finding the evidence sufficient to show that someone had given the patients large overdoses, and the United States Supreme Court declined to hear the case in 1993. That year Diaz went to court in New York to obtain the records behind a large study of lidocaine concentrations in human tissue held by a New York county medical examiner. New York's highest court ruled in November 1993 that he had a substantial interest in the records, because they might enable him to show that he had been convicted and sentenced to death for murders that did not occur. No court ever set his convictions aside.
He was never executed. Diaz died of natural causes in August 2010, at seventy-two, at a hospital near San Quentin, after twenty-six years on death row. Published accounts give the date as August 9 and as August 11.