A new study of cult murders in the U.S. suggests that even the deepest and most disturbing convictions are no proof of mental illness—nor, some argue, should they be.

Charles Manson en route to his sentencing hearing, March 1971. (Photo: AFP/Getty Images)

Cults are viewed as both sinister and strange. We associate them with gruesome violence, bizarre delusions, and perverse spirituality. Even if not all cults are sinister, the label becomes a way to distinguish more common religious beliefs from the more exotic ones.

But where does distinction become a diagnosis? Do cult beliefs, for example, qualify as psychotic? Are some so strange that adherence ought to be taken as proof of a neurochemical dysfunction? That question is the center of a paper entitled "Killer Cult Members and the Insanity Plea: Exploring the Line Between Belief and Delusion," published this month in the Journal of the American Academy of Psychiatry and Law.

Dr. Brian Holoyda of the University of California–Davis examined eight cases of cult murder in the United States beginning with the Mansons in 1969. He found that, in four of these cases, the defendants had pleaded not guilty by reason of insanity (NGRI) and, of those, only two received psychiatric diagnoses—one with paranoid schizophrenia, another with a shared psychotic disorder. Neither was successful.

"Someone could testify that a cult member was so beaten and broke by their cult that they simply did whatever they were told to save their lives or to protect themselves."

While Holoyda acknowledges that such cases are extremely rare, he concludes that American courts ultimately view cult beliefs—even those that have driven people to murder—as voluntary, no different from religious belief. He points to one ruling in particular: the 1999 trial of Jacques Robidoux in Massachusetts, where Robidoux deprived his infant son of all solid food based on a revelation Robidoux had received from God. The boy starved to death.

"In our diverse religious cultures, Christian Scientists are often committed to resist conventional medical treatment in situations even where the results can be dire, and Jehovah's Witnesses may oppose blood transfusions even where doctors say this is essential," wrote the presiding judge.

Because the legal system rarely treats these beliefs as representing insanity, the judge ruled that Robidoux's case would be no different. Nor, apparently would it have been in any other state.

To the layperson, the first two cases Holoyda presents may seem especially unusual: the murders of 26-year-old James Thimm and five-year-old Luke Stice at the hands of Michael Ryan and his 15-year-old son Dennis.

Michael Ryan was the leader of a cult based on the Stice farm in Rulo, Nebraska. He claimed to channel the spirit of an archangel and made wild claims about the impending battle of Armageddon. When police raided the cult, they found evidence of preparation for such a battle: 150,000 rounds of ammunition, 30 semi-automatic rifles, 15 machine guns, more than a dozen pistols, and $250,000 worth of stolen farm machinery.

The cult's divine directives were confirmed through something called "the arm test." One of the group members would hold out their arm while another member, usually Michael Ryan, would hold their wrist and shoulder, forcing it down like a lever. If the arm yielded to questioning, Yahweh's answer was no. If it held up, the answer was yes. "Every detail of every activity at the farm was determined by consulting Yahweh through ... the arm test," the court syllabus says.

Sometime in early 1985, several members of the group, including Thimm, Luke Stice, and his father, Rick, fell out of favor with Yahweh. Michael Ryan began torturing them, often forcing Rick to beat his own son and using the boy's mouth as an ashtray. Luke died after Michael Ryan shoved him into a shelf and hit his head. When Ryan forced Rick to dig the grave, Rick fled, leaving two of his other children behind on the farm.

At this point, the Ryans turned their attention to Thimm. He was shot in the face and, while horribly injured, forced to have sex with a goat. Michael Ryan sodomized him with a shovel handle, shot off his fingers, and skinned him alive, slicing flesh from his leg and peeling it off with pliers. Thimm finally succumbed when Michael Ryan stomped on his chest and Dennis shot him in the head.

As the court syllabus reads:

[Michael Ryan's attorneys] were faced with the almost impossible task of defending a man who had repeatedly committed various acts of most horrible torture upon another human being; who did these acts in the name of an angry deity; who heard this deity speak audibly to him; who believed that every aspect of his life, as well as the lives of others in the group was directed by that deity through an arm test; who believed he possessed the spirit of an archangel; who believed he could predict the future and read the minds of others in the group; who saw visions in the sky; who believed that a female group member's infant had been divinely conceived....

As one of the men tasked with defending him, Richard Goos, would testify at a post-conviction hearing "the man was obviously either insane or he was unbelievably cruel and subhuman."

Michael Ryan was examined by a clinical psychologist, Dr. Maurice Temerlin, and a psychiatrist, Dr. Wingert, both hired by the defense. Temerlin testified that Ryan suffered from paranoid schizophrenia and believed he was "doing a virtuous deed" when he murdered Thimm. Wingert testified that Ryan believed it was "something commanded by God" and that "he was obligated to obey." Wingert also described Ryan as "clearly delusional" and "not under the influence of any kind of cognitive control."

The two prosecution experts, however, didn't agree. They found that Michael Ryan did understand the nature and likely consequences of his actions. The jury sided with the prosecution and sentenced him to death.

As for Dennis Ryan, he was found to have suffered from a shared psychotic disorder under the influence of his father. Still, the psychological experts believed that at the time of the crime he was capable of distinguishing right from wrong. The jury convicted him of second-degree murder, which, after climbing to Nebraska's Supreme Court, would eventually be reduced to manslaughter. He was released from prison in 1997, 12 years after he was convicted in 1985.

Dr. Michael First is a forensic psychiatrist at Columbia University and one of the authors of the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, the de facto bible for psychiatrists. He's testified in a number of high-profile cases regarding religiously motivated violence, including that of fundamentalist Mormon Ron Lafferty, and of Zacarias Moussaoui, the so-called 20th hijacker who was arrested before the 9/11 attacks.

First says he isn't at all surprised the NGRI plea failed in the cases Holoyda examines. While a good defense attorney will flag unusual beliefs as hints of an underlying mental illness—what First calls "the tip of the iceberg"—simply holding those beliefs doesn't begin to check the boxes required for a diagnosis. According to Dr. Paul Appelbaum, one of the nation's leading forensic psychiatrists (and a colleague of First's at Columbia), a few of those boxes include evidence of heritability, susceptibility to treatment, or a natural history that aligns with the clinical understanding of the progression of an illness.

In Moussaoui's case, First found several markers of mental illness, but they had nothing to do with his religious beliefs. Rather, they were deluded proclamations that George Bush would set him free. There was also the telling fact that other members of Moussaoui's family suffered from psychotic disorders.

Still, even with a diagnosis, securing an NGRI verdict is a moonshot. Most of the work involves proving the disorder interfered to such an extent that the cult member was unable to distinguish right from wrong at the time of the crime, according to Appelbaum. On this point, mental health experts very rarely reach a consensus.

"This is fairly nuanced thinking to be able to wade through these things," First says. "You can easily imagine how different experts might disagree on these conclusions." The fact is that the vast majority of violence is not the result of mental illness, First says, adding that history is full of examples of evil individuals who betray zero clinical evidence of any sort of psychological defect. Yet it's hard to abandon the idea that certain crimes are so inexplicably and horrendously bizarre that no sane person would commit them. Whatever the courts say, colloquialisms about a particular brand of criminal being "insane" exist for a reason.

Not all religious beliefs are mere variants of human behavior. There are such things as "religious delusions," but these are difficult to identify because they—like other religious beliefs—aren't falsifiable.

You can provide evidence to disprove that the Federal Bureau of Investigations is tapping into the phone of a paranoid schizophrenic, for example. If the paranoid schizophrenic rejects that evidence, you have a clear indication that he or she is deluded. Here's where religion makes things tricky: "If God or whatever told them to do it how can you disprove that?" First asks.

"Religion is the standard," First continues. "If anything, having very strong religious beliefs is normal. So at what point can you say that someone with a very strong religious belief is not normal? How extreme does it have to be?" That elusive (and touchy) distinction is why, to Appelbaum's knowledge, neither religious fanaticism nor cult belief has been seriously considered for its own distinct category in the DSM.

But the last two editions of the DSM both mention cults. In the fourth edition (issued in 1994), cults are referred to under Paranoid Personality Disorder; in the fifth (issued in 2013), cult involvement was listed as a potential cause of "identity disturbance due to prolonged and intense coercive persuasion." Other such causes included brainwashing, thought reform, indoctrination, long-term political imprisonment, and recruitment by terror organizations.

Holoyda suggests that, under this relatively new definition, cult involvement would serve more as a mitigating factor in a criminal case rather than proof of genuine psychosis. "Someone could testify that a cult member was so beaten and broke by their cult that they simply did whatever they were told to save their lives or to protect themselves," Holoyda says.

Both definitions contain only traces of what is arguably at the heart of the question: the possibility of choice. While First objects to this as a means of distinguishing the sane from the insane, Appelbaum feels it is as close as anyone is likely to get to summing up the difference between a psychiatric disorder and an insane-seeming religious belief. And until the courts or profession of psychiatry are ready to wade into the debate on free will, that may be where the questions should stop.