Some past cases in the United States involving nurses or nurse's aides who have been charged with killing patients:

— July 2001: Ex-nurse Kristen Gilbert sentenced to life for murdering four patients at Veterans Affairs Medical Center in Northampton, Mass. Injections of epinephrine made victims' hearts race out of control. Prosecutors say she did it for thrill of creating medical emergencies.

— May 2000: Former nurse Rhea R. Henson given suspended two-year sentence for administering morphine overdose to two terminally ill patients at Inova Fair Oaks Hospital in Fairfax, Va.

— October 1999: Former nurse Orville Lynn Majors convicted of six counts of murder for giving lethal injections to ailing patients at Vermillion County Hospital in Clinton, Ind. Sentenced to 360 years.

— January 1990: Nurse Richard Angelo of Lindenhurst, N.Y., sentenced to 50 years to life for killing four patients by injecting paralyzing drug so he could revive them and appear a hero.

— August, November 1987: Donald Harvey, former nurse's aide, pleaded guilty to at least 34 murders in Ohio and Kentucky; serving life in prison. Most victims were patients at Drake Memorial Hospital in Cincinnati or Marymount Hospital in London, Ky.

— September 1986: Nurse Terri Rachals acquitted of killing six patients at Phoebe Putney Hospital in Albany, Ga., by injecting potassium chloride, which in high amounts can cause cardiac arrest. Found guilty but mentally ill on one of 20 charges of aggravated assault.

— March 1984: Coronary-care nurse Robert Diaz convicted of killing 12 elderly patients with lethal doses of heart drug in March and April 1981. Eleven victims were at Community Hospital of the Valleys in Perris, Calif.; 12th was at San Gorgonio Pass Memorial Hospital in Banning, Calif.