"They're insane."

"Only a total lunatic, a psychopath, would do such a thing."

"How sick is that?"

"You've really got to be crazy."

You hear sentences like these on a daily basis, from friends and colleagues, in newspapers and on TV. Internet forums are full of them. It's common knowledge, after what happened in Nice, Würzburg, Munich, Ansbach — these very different, but all highly disconcerting crimes — that the Tunisian guy with the truck, the boy with the axe, the person running amok with the gun and the guy with the backpack full of explosives all must have mental issues.

But how does this categorization help? Not at all, according to forensic experts. "Of course, it's a common colloquialism to call the guy who blows himself up in the middle of a crowd insane," says one German psychiatry professor. "In that sense, the Nazis were crazy, too. But from a clinical and legal point of view, this pathologizing doesn't work at all."

Calling these offenders crazy is a natural thing to do: the pathologization of their crimes is an attempt to make some kind of sense from the incomprehensible. Naturally, it also blurs the culprit's image, involuntarily relieving person of responsibility. Thinking that someone who commits such a horrible crime must be mentally ill, and therefore considering the crime itself proof of the offender's mental incapacity, is as old as criminality itself. It's the strategy employed by lawyers everyday to save their clients from conviction.

In those attributions of insanity, which are often false, one can see society's degree of preconceptions concerning mental illness. If someone's "somehow strange," sad or disturbed, full of hate, he or she might conceivably lose it at some point. Some commentators don't hesitate to openly draw connections between depression and going berserk.

The consequence of such opinions is the stigmatization of those who are truly ill. And it's unclear whether the depression David S. in Munich was treated for eventually led to his rampage. Experts know that depression usually leads to withdrawal, listlessness, torpidity and suicide rather than deadly aggression towards others.

"It's highly unlikely that the culprit's depression is the reason for his act in Munich," noted Ulrich Hegerl, a chair of the German Foundation for Depression Relief.

But such distinctions are blurry. At the Würzburg Clinic and Polyclinic for Child and Adolescent Psychiatry, Psychosomatic Medicine and Psychotherapy, professor Marcel Romanos sees a dangerous trend of "continuously equating mental illness with sociopathy and being a danger to the public." Doing so is absurd considering that in Germany, one in three people suffers from a mental illness at some point, but most never become dangerous.

On the other hand, in his book Social Anxiety Disorder, fear researcher Borwin Bandelow observes that "many terrorists are the result of their paranoid personality disorder." He also differentiates among narcissistic, antisocial and paranoid terrorists. The narcissists want to go down in history as heroes; the antisocial hide their pleasure in killing behind ideology; and the paranoid feel persecuted by the world. Bandelow further explains that a terrorist with a borderline personality could become a dangerous suicide attacker out of impulsivity.

Reproachful conclusions

All of this obviously does not explain how strong a personality disorder is and to what extent it can be held responsible for a specific attack. The greater the disorder, the lesser the perpetrator's responsibility. The case of Norwegian mass murderer Anders Breivik shows how delicate using the scales truly is, even for experts.

The first expert opinion in 2011 declared Breivik paranoid, schizophrenic and certifiably insane during the attack. A second opinion claimed he indeed suffered from a narcissistic and antisocial personality disorder, but said he was not mentally ill to an extent that would justify what he had done. Breivik went to court and was convicted.

Breivik standing trial in Oslo District Cour on April 16, 2012 — Photo: Hakon Mosvold Larsen/Xinhua/ZUMA

Youth psychiatrist Romanos notes that such cases are extremely rare. "Only a few mental disorders lead to exemption from criminal responsibility," he says. Psychiatrists estimate that nearly half of Germany's inmates are mentally ill. Some prisoners suffer from personality disorders with an obvious lack in empathy; others are violent criminals with antisocial traits. And yet all are criminally liable. Otherwise they'd be in an asylum, not in prison.

That's what's so problematic about stereotyped thinking when it comes to mental illness. Every time the public finds out that a criminal like David S. in Munich had been undergoing psychological treatment, critics quickly come to reproachful conclusions: Why didn't anybody notice anything? How could they let him go free?

Germany's major youth psychiatric facilities treat thousands of patients each year, about one tenth of whom are hospitalized. Some obviously have violent tendencies. But if you tried to lock away in a psychiatric institution anyone who might one day become a threat — a move that is, incidentally, out of step with the times — there would be no room for all the patients. If there's only the slightest doubt about the propensity of certain individuals for violence, the same critics often claim, then you're locking them away unscrupulously, treating them like dangerous maniacs.

The theory of mental illness as a cause of terrorism further misjudges the influence of social structures and peers. Without trying to compare the incomparable, the Nazis' killing was, to the victims of that time, nothing more than what today's Islamic terror is to us: a series of incomprehensible atrocities, committed by people who clearly live in a psychic universe that shuns all rules of morality, sanity and peaceful cohabitation.

The degree of brutality that is required for a human being to beat Jewish children to death or kill dozens of innocent people with a truck, as happened in Nice, is hard to bear, as is the carnage in civil wars all over the world. The so-called evil isn't a medical category.

Paradoxically, calling the culprits "maniacs" has backward consequences. It makes the guilty not legally responsible. Today's terror doesn't work that way, and neither did the racial fanaticism of the Nazis. Their devastating racial madness was, of course, delusional. When in 1941 the Nazis killed 33,000 Jewish civilians, they were following a construct of ideas that was completely detached from reality. And young people who learn about the crimes of the past ask the same questions when faced with the horrifying acts that have shocked the Western world recently: How can people do such things? How sick do you have to be?

The answer is disconcerting: Not sick at all. You don't have to be mentally ill to commit horrible crimes. Ideology makes people do things the rest of the world considers delusional. According to the system the doer is in, the person's behavior is normal, even heroic. That's why suicide attackers take as many people as possible with them. According to their logic, this is the best way to head for paradise. In the mass-murder dynamic of the Nazis, people who killed thousands of Jews proved themselves "decent human beings," in the words of Nazi leader Heinrich Himmler.

Psychiatrist Romanos has recently witnessed a whole different form of mental suffering in Würzburg. Many unaccompanied young refugees have been hospitalized because they are at risk for suicide. "These are traumatized young people other teenagers now accuse of being sleepers and terrorists," he says. "And that kind of psychological strain has become almost unbearable for them."