PHILADELPHIA - What goes on in the minds of medical professionals who become serial killers?
Forensic experts are trying to answer that question following the arrest of Charles Cullen, the New Jersey nurse who says he killed as many as 40 patients. He has been charged with murder in the death of one patient, and investigators are looking into deaths at 10 Pennsylvania and New Jersey hospitals where Cullen worked.
Since 1974, nearly four dozen nurses, therapists and doctors have been prosecuted for serial killings in the United States and other countries. The phenomenon is becoming more common or is being detected more often.
Yet unlike sexual predators who become serial killers, caregiver-slayers do not seem to have a characteristic psychological profile, family background or pattern of experiences.
What they do have in common is a pathological self-centeredness, says Beatrice Crofts Yorker, a lawyer and nurse who has studied dozens of cases.
"They think of meeting their own needs ahead of the needs of all others," said Yorker, director of the nursing school at San Francisco State University.
Those needs, experts say, tend to fall into three categories. The killers could be seeking a sense of power and control. They might be trying to get attention and respect by staging medical emergencies, much like firefighter-pyromaniacs who crave praise for putting fires out. Or, health-care killers might just need to be cruel.
"The person is just a sadist," said N.G. Berrill, a professor of forensic psychiatry at John Jay College of Criminal Justice in New York City.
That sadism might not become deadly until the health-care worker faces a whiny or uncooperative patient, said Michael Welner, a New York City forensic psychiatrist who developed a scale for judging the depravity of a crime.
"They have contempt for the patient. But they don't see themselves as homicidal serial killers," Berrill said. "In their own minds, they've done something righteous. They may even justify their actions as merciful."
While such behavior is sociopathic, it is not insane or psychotic, Yorker said. Psychotics are delusional and lose touch with reality.
"These people are not disorganized," she said. "They go for lengthy periods doing high-level work."
Some killers are quite methodical. Nurse Richard Angelo, convicted of killing four patients on Long Island, N.Y., practiced by giving near-toxic doses of medications to field mice.
Cullen, who claims to have killed more than 30 patients, is unusual in having confessed after his arrest, Yorker said: "Of the 42 cases I've studied, only three killers confessed."
She has not found any common traumas, such as child abuse or watching parents suffer terminal illness, in the backgrounds of health care killers.
However, she has found a common thread: A history of pathological lying that often goes back to childhood.
As adults, many of them falsify their credentials or patient records. They also typically kill using readily available injectable medicines, and they work odd shifts in varying areas.
Given the complex, ambiguous nature of their psychological dysfunctions, they are not easy to screen out during a hiring process, experts agree.
The best ways to reduce the danger of serial murder are careful surveillance and quick action in suspicious cases. Unfortunately, Yorker said, some hospitals would rather cover up than confront a problem.
"In [an] Indiana case," Yorker said, "the head nurse who blew the whistle was fired, then reinstated, but by that time had severe stress-related symptoms. She will never work as a nurse again."