In 2021, a group of experts led by Juan Méndez, the former UN Special Rapporteur on Torture, examined interrogation practices in the context of criminal investigations. The result are international guidelines – commonly known as the Méndez Principles. At their core, they advocate for a fair, respectful treatment of defendants, victims and witnesses, with open questions instead of leading questions and without applying psychological pressure.

In this way, they guide the police, public prosecutors and courts in questioning people in such a way that they receive more reliable information and avoid false confessions. The most important foundations of the Méndez Principles are human rights and scientific findings on questioning techniques. Specific recommendations include audio and video recordings of interviews – still a rarity in Switzerland – as well as special consideration for vulnerable groups such as children, traumatised people or people with cognitive and language difficulties.

The Mendéz Principles will now also be the subject of discussion in Switzerland at the 10th symposium on police law on 13 March 2026, which brings together law enforcement experts to meet at the University of Bern.

uniAKTUELL: Jonas Weber, as an academic, you deal with the practice of questioning in criminal proceedings and read a large number of transcripts of interrogations by the police, public prosecutors and courts. What has caught your eye?
Jonas Weber: That they often ask close-ended questions or questions that already makes an assumption on the course of events. This is a type of questioning that is not only biased, but also counterproductive. The person doing the questioning shouldn’t colour their questions with their own assumptions. They have to give the person being questioned the chance to remember events on their own. The question must not override the person’s memory or steer it in one direction. Open questions are therefore key.

How else can interrogation or questioning practice be done better in Switzerland?
There are a lot of interruptions, impatience is a big factor. When a judge, for example, interrupts a witness or suspect and says “that's not relevant”, this is not conducive to getting to the truth. I have the impression that specialized police officers are often more sensitive and patient in their questioning than courts, especially when it comes to sexual and violent crimes.

The length of the interrogation also plays a role. There are studies that show that a person should not be questioned for more than four hours at a time. In Switzerland, however, we repeatedly have significantly longer interrogations. The answers can then become less reliable because the person being questioned become tired and unfocused and may answer in such a way that would finally being the interrogation to an end.

«In Scandinavian countries, audiovisual recordings are part of everyday working life in law enforcement. The court can listen to everything that happens in police interrogations – not so in Switzerland.»

Jonas Weber

So there is a lot of pressure during questioning here?
Yes, for example when an accused person is threatened with an extension period of time in custody before even getting to atrial, or with having their mobile phone investigated, which could bring evidence of other crimes to light. In my view, this is often not professional. It can encourage false statements and make the accused less cooperative because they lose trust in the criminal investigation authorities. In principle, no situations should be created that put pressure on the person being questioned.

What else speaks in favour of adhering to the Méndez principles?
The clearance rate for sexual offenses in Switzerland is only ten percent. If we want to improve this rate, we need to create an empathetic and respectful situation for victims from the outset. Right from the first interview at a police station, we need to comply with the Méndez principles. In my opinion, this would lead to more reliable statements for the investigation of criminal cases and more victims agreeing to come forward and press charges against their assailants.

«More harshness during interrogations or in custody does not lead to more cases being solved.»

Jonas Weber

Why are interrogations in Switzerland generally not recorded at the moment, so that there is usually only a written record?
In my opinion, the lack of audiovisual documentation of interrogations is the biggest problem in Switzerland. Well over 90 percent of all interrogations are not recorded, which is difficult to understand. I find it problematic when a court cannot check how an interrogation actually went. Also because the information on non-verbal communication between the questioner and interviewee is lost. In the Scandinavian countries, audiovisual recordings are part of everyday working life in law enforcement. . The court can listen to everything that happens in police interrogations – not so in Switzerland..

At a political level, there are many calls for more rigor, especially when it comes to vulnerable people such as those with temporary residence status.
More harshness during interrogations or when a suspect is in custody awaiting trial does not lead to more cases being solved. It has been empirically proven that it is not harsher punishments, but rather a higher clearance rate that leads to fewer people becoming criminals. Politicians and authorities need to understand that applying the Méndez principles ultimately leads to fewer crimes.

«To be honest, I suspect that the law enforcement authorities are afraid of being themselves subjected to oversight.»

Jonas Weber

One example: foreign-language speakers should be able to count on a good-quality translation. The authorities should also be transparent with people who do not have Swiss citizenship as to whether the interrogation could affect their residence status. Such information is essential for refugees who are questioned as witnesses, for example.

How can the Méndez principles actually be applied in Switzerland?
The Swiss tradition is to leave the application of new guidelines to the authorities themselves and not to turn them into binding legal norms from the outset. In principle, however, parliament could amend the Code of Criminal Procedure in such a way that the application of the Méndez guidelines becomes binding.

«In Switzerland, we do not have mandatory further training for court personnel. They are often the last to learn about such international recommendations.»

Jonas Weber

In practice, the courts may have to require public prosecutors and the police to comply with the Méndez principles. But it is also important to know that we do not have mandatory further training for court personnel in Switzerland. They are often the last to learn about such international recommendations.