INTERVIEW - After the homicide in Berikon, a child psychiatrist says: "Frustration alone does not turn healthy children into murderers."

A 14-year-old is suspected of killing a 15-year-old girl in Berikon, Canton Aargau, on Sunday. Dorothea Stiefel treats juvenile offenders at the Center for Child and Adolescent Forensics at the Psychiatric University Hospital of Zurich. A conversation about how children become criminals and when they are criminally responsible.

Ms. Stiefel: What conditions, feelings, or whatever can lead a young girl to commit such a crime?

Such crimes don't come out of the blue. There are always certain preconditions. As doctors, for example, we would check whether the girl has any genetic defects that could make her particularly impulsive and violent. Such crimes are also favored by social factors, for example: children who grow up in an environment where they experience a lot of violence or learn to use violence as a problem-solving strategy are more likely to become perpetrators. And there are certain psychological conditions in which such crimes are more likely to be committed: a drug high, for example, or an acute psychosis in which children lose touch with reality.

But there also needs to be an acute trigger?

Exactly. Situational factors can also play a role in such crimes. Bullying or a lack of recognition, for example, can put a child under extreme emotional stress. In Berikon, there was allegedly an argument between the girls beforehand. But frustration alone doesn't turn healthy children and adolescents into murderers. Or only very, very rarely. Typically, the child must be psychologically destabilized by one or more preconditions.

At 14, you're in the middle of puberty. Are adolescents particularly at risk?

Yes, absolutely. Such an act requires incredible impulsiveness. And during puberty, the frontal lobe, which is responsible for controlling our actions, isn't yet sufficiently developed. This process is usually not completed until our mid-twenties. Adults sometimes get angry or frustrated, but they activate their prefrontal lobe and stop the process. Children and adolescents don't yet have their impulses as well under control. In such situations, they lash out more quickly or sometimes even resort to a knife.

But younger children also have an immature frontal lobe. Why are they less likely to commit crimes?

Children during puberty develop a need to test boundaries and prove themselves to the group. They are sometimes tempted by others to do things they would never do as an individual. The problem: During puberty, we are already relatively cognitively developed: We have ideas, we want to act. However, we control our thoughts and feelings more slowly than we act, because our impulses to act are still too weakly controlled. The proportion of juvenile delinquents is therefore highest during this phase, but most end their criminal careers by the end of adolescence.

In Switzerland, 14-year-olds are already considered criminally responsible, but are subject to juvenile criminal law. Can such a child even understand what they are doing?

With a mentally healthy teenager, one should assume that they can fundamentally distinguish between good and evil. But that only applies to normal situations. When children or adolescents are overwhelmed by their emotions, they often enter a state of emergency and confusion. "I just saw red back then," some of the young people who come to us tell us. It requires not only understanding what a crime is, but also the ability to control oneself so as not to commit it in the heat of the moment.

Almost two years ago, a similar case caused a stir. Two girls in Germany stabbed a girl of their own age to death—one of them allegedly even planned the crime. At the time, an investigator said something like: "Adults can't understand children's motives for such acts." Is that true?

Yes, absolutely. Precisely because we adults have better control over our emotions, it's hard for us to understand how a school conflict or rejection by a friend can put such a strain on someone's mental health. So much so that they commit such an act. For such a planned act to occur, a child must be so extremely depressed and desperate that the distinction between good and evil is temporarily irrelevant, or they have lost touch with reality. But such things tend to be the exception, especially among girls. Emotionally motivated and impulsive acts are much more common.

When is a child criminally responsible?

First of all, you have to know: Criminal responsibility always relates to a specific act, not to the person in general. In order to assess it, a doctor has to check various things. Firstly, is the child capable of understanding? Is they able to distinguish between good and evil? This is not always the case, for example, with a child of very low intelligence. Secondly, to what extent was the child able to control their own impulses at the time of the act? Was the child under the influence of drugs, for example, and therefore only partially capable of understanding? And thirdly, how is the child's general maturity developing? Is the child significantly behind other children of the same age? If the answers to all three questions are: The child is not particularly conspicuous, then they are fully criminally responsible for the act.

Does that mean it can be convicted of this crime?

Yes. What's special about juvenile criminal law in Switzerland, however, is that it's primarily about helping the offender, not punishment. To this end, however, children are subjected to measures that can be ten times more severe than those associated with a prison sentence. It's not uncommon for young people here to say, "I'd rather go to jail; at least I'll have some peace and quiet there." In a therapeutic facility, they are challenged: They have to attend therapy regularly and are integrated into a daily routine and a community. They must learn to adhere to socially accepted norms. Many also begin vocational training.

Can a prison sentence deter children?

For minor offenses like theft, the threat of a prison sentence can actually be a deterrent. However, the young people we usually have here are repeat offenders. They come for property damage, robbery, repeated theft, or assault. For them, a prison sentence alone is no deterrent. The same applies to young people who become murderers. Because they're not thinking about it at the time. At the same time, research shows that if you only put juvenile offenders in prison, most of them will become even more criminal.

How good are the chances of successfully reintegrating these children?

I can't say for the specific case; I don't know the case well enough. But generally speaking, the earlier a child commits crimes, the more difficult the integration process becomes. Likewise, every juvenile offender has so-called turning points—events that can stabilize them or, conversely, derail them. These can be new friends, a caring soccer coach, or even professional success. Events that boost self-esteem.

And vice versa?

Can turning points that damage self-esteem lead to another decline? For example, if the adolescent is expelled from school? Such experiences are difficult to predict, which makes individual prognoses so challenging. But if a child is well-established in life, if they are of normal intelligence and psychologically and genetically healthy, if they have caring parents and have been treated successfully by professionals, there is little reason why an expert would then say: This girl is still dangerous.