Minnie Lee Dempsey, an 88-year-old woman, entered the cardiac care/intensive care unit at Community Hospital of the Valleys in Perris during the night of April 5, 1981, suffering from chest pain, shortness of breath and congestive heart failure. Despite those medical problems, she was conscious and able to speak when she arrived. The night shift was being worked by registered nurse Robert Rubane Diaz and nurse Carl Chetlan. The events that unfolded during the early morning hours of April 6 would later become part of the murder case that identified Dempsey as one of a series of hospital patients deliberately poisoned with lidocaine.
About half an hour after Dempsey was admitted to the ICU, at approximately 4:39 a.m., she suddenly went into violent seizures, followed by respiratory and cardiac arrest. Hospital personnel managed to revive her, but the seizures continued for roughly 15 minutes before she was stabilized and placed on a respirator. During the same night, another patient, Helen Primakow, experienced remarkably similar seizures but survived. Chetlan later described the episodes affecting both patients as extraordinarily violent, involving their entire bodies. The unusual nature of these seizures would become important because nurses at the hospital were witnessing the same frightening pattern in multiple cardiac patients during the weeks Diaz worked the night shift.
Dempsey suffered another cardiac arrest at approximately 6:32 a.m. and was again revived. When day-shift nurse Lyn Race arrived at about 7:00 a.m., Diaz told her what had occurred during the night and predicted that Dempsey was going to “code,” meaning that she would suffer another life-threatening emergency. Race later described Diaz as unusually excited and hyper, pacing rapidly between Dempsey's room and the nursing station. While the incoming nurses were receiving their shift briefing, Diaz remained with the patients and interrupted the meeting to call for emergency assistance. Race hurried to Dempsey's bedside and found her experiencing additional seizures. Her heart stopped shortly afterward, and she died at 7:18 a.m. on April 6, 1981.
At first, Dempsey's death could have appeared to be the tragic end of a patient already suffering from serious heart disease. That became increasingly difficult to accept as similar emergencies and deaths accumulated in the ICU. Diaz had begun working the hospital's night shift on March 29, and over the following weeks at least 13 patients on the night shift suffered violent seizures generally followed by respiratory or cardiac arrest. Nine died at the Perris hospital. Nurses testified that the episodes resembled grand mal epileptic seizures and were unlike anything they normally saw among cardiac patients. Authorities eventually began investigating what appeared to be an extraordinary concentration of deaths.
The investigation focused on lidocaine, a legitimate cardiac medication that can help control dangerous disturbances in heart rhythm when given in proper amounts but can be fatal in massive doses. Prosecutors ultimately alleged that Diaz manipulated preloaded lidocaine syringes so that patients received concentrations many times stronger than intended. According to the prosecution's theory, a syringe that ordinarily contained a 2-percent lidocaine solution could be emptied and replaced with a 20-percent solution, allowing approximately 1,000 milligrams or more to enter a patient's bloodstream within minutes. Expert witnesses testified that such a dose could be lethal.
Dempsey's medical evidence became a significant part of the prosecution's case. Dr. Roy Jutzy, who reviewed her records, testified that cardiac rhythm strips following her first seizure displayed an abnormally broad QRS complex consistent with a large dose of lidocaine. Toxicologists Michael Peat, Alphonse Poklis and Randell Baselt examined the quantities of lidocaine discovered in her tissues and concluded that she had received one, and possibly two, massive overdoses. Pathologist Dr. Rene Modglin attributed her death to lidocaine poisoning, while identifying hypertensive arteriosclerotic heart disease as another significant medical condition. The prosecution maintained that the quantity of the drug and the timing and severity of Dempsey's symptoms could not be explained by routine therapeutic treatment.
Diaz's defense disputed that conclusion. Defense experts offered several alternative explanations, including the possibility that another medication, aminophylline, contributed to the first seizure, that an impaired blood supply to the brain following treatment with Valium played a part in subsequent seizures, or that Dempsey ultimately died from a heart attack. A defense pharmacokinetic expert also argued that the amount of lidocaine detected in her tissues could be consistent with medication administered therapeutically. Prosecutors countered those opinions with the cardiac evidence, toxicology results and Dempsey's clinical symptoms. The courts ultimately concluded that there was substantial evidence establishing that Diaz killed Dempsey by injecting her with a lethal overdose of lidocaine.
Suspicion surrounding Diaz extended beyond Dempsey's death. After the Perris ICU was closed, Diaz obtained work at San Gorgonio Pass Memorial Hospital in Banning, where another patient died after developing symptoms similar to those seen in Perris. Investigators examined dozens of suspicious hospital deaths across Southern California. On May 1, 1981, authorities executed a search warrant at Diaz's home. Among the items seized were syringes, an empty lidocaine box and lidocaine itself. Police found a half-empty vial containing a 20-percent lidocaine solution in a discarded bag along with syringes, as well as a sealed vial of the drug inside a bedroom closet. These discoveries became part of the circumstantial case connecting Diaz to the hospital poisonings.
Diaz remained under investigation for months while authorities conducted autopsies and sophisticated toxicological testing. He was arrested at his Apple Valley home on November 23, 1981, and ultimately prosecuted for 12 murders. A formal California complaint charged him with 12 counts of murder and sought the death penalty. The case was unusually complex, involving extensive medical testimony, laboratory analysis, hospital records and testimony from nurses who had worked alongside him during the fatal shifts.
Diaz waived his right to a jury, leaving Riverside County Superior Court Judge John Barnard to decide the case. The trial began on October 31, 1983. On March 29, 1984, Barnard found Diaz guilty of all 12 murders, including the killing of Minnie Lee Dempsey, and also found the multiple-murder special circumstance proved. Prosecutors argued that the deaths were intentional poisonings, while the defense continued to maintain that the patients had died naturally or as a result of complications and legitimate medications. No definitive motive was established at trial.
On April 11, 1984, Judge Barnard sentenced Diaz to death after rejecting a defense request for life imprisonment without parole. The California Supreme Court later reviewed the case automatically because it involved a death judgment. In 1992, the court upheld all 12 first-degree murder convictions and the death sentence, while striking 11 redundant multiple-murder special-circumstance findings for technical legal reasons. The ruling specifically upheld the finding that Dempsey had been murdered through lidocaine poisoning. Diaz continued to maintain his innocence and remained under a sentence of death rather than being released or having the murder convictions overturned.
Diaz was never executed. He remained imprisoned on California's death row for decades while litigation continued. On August 11, 2010, he died of natural causes while still under the death sentence. His death ended the criminal proceedings against him, but the convictions remained intact. Minnie Lee Dempsey's death, once occurring amid what appeared to be a succession of medical emergencies in a small hospital ICU, ultimately stood as one of the 12 murders for which Robert Rubane Diaz was convicted.
