The voice is the new fingerprint. A drop of sweat is the better testimony. The virtual crime scene more accessible than the real one. Laser instead of tape measure. Robots instead of forensic doctors. Swiss investigators rely on high-tech – and thus expose almost every killer.
The Institute of Forensic Medicine at the University of Zurich is the test laboratory in Switzerland and even the world when it comes to new technologies in forensics. Anyone who dies in Zurich, Schaffhausen or Central Switzerland in an inexplicable, sudden or violent way ends up here. Over 1000 dead were examined at the institute last year.
Head Michael Thali (53) receives a view of the tour. It leads into a room in the basement. A robot arm, the Virtobot, hangs from the ceiling. Underneath is a computer tomograph, i.e. an X-ray machine. In addition, a scanner consisting of several cameras, the Virtoscan.
Autopsy of the corpse without a cut
The machines can autopsy a corpse without damaging it. Within seconds, they create an image of the corpse – three-dimensional. The recordings provide information about the cause of death. In the case of a crime, also on the course of events and the weapon.
Radiology technologist Dominic Gascho explains: “The special cameras on the Virtoscan not only depict the surface as we know it from conventional cameras. We get deeper under our skin with it. ” Depending on the camera setting, injuries under the skin that cannot be seen from the outside are visible. Or traces of foreign body fluids on the body – especially important in sex crimes. Or smoke traces that occur when a shot is fired.
Gascho: “In the case of gunshot wounds, we quickly find the projectile in the body with the computer tomograph and can assign it to certain metals – without removing it.” The device shows even the smallest injuries on the bones. In the case of a headshot, the direction and the angle from which the projectile was fired can be determined.
The advantage of the Virtopsy: the body remains intact and the 3-D image can be reused. “In the course of an investigation, you can consult the scan again and perhaps recognize new clues,” says Thali.
Back to the crime scene with 3-D glasses
Nowadays forensic scientists not only make 3-D models of victims – but also of entire crime scenes. For example, a laser device scans the apartment in which someone was shot in the process of securing evidence. Every piece of furniture is recorded, carpet, every glass, every shard. A virtual crime scene is created on the computer.
And it has even been possible to visit it for a few years: together with the Forensic Institute of the Cantonal and City Police of Zurich (FOR), the University of Zurich has developed virtual reality glasses. It enables the wearer to re-commit the crime scene.
The glasses help to check the statements of witnesses and those involved in the crime: Did the eyewitness really have a clear view of what was happening or was an object blocking his way?
Investigators at the crime scene still have to secure fingerprints and DNA samples. They then land back at the University of Zurich and are examined, among other things, in the field of forensic genetics.
Compare DNA, not decipher it
The potential of these samples is high. Because a person leaves DNA everywhere: It can be found in every drop of saliva or sweat, in every hair and in every flake of skin. Forensic doctors are currently only allowed to compare DNA traces – and not decipher them.
Specifically, this means: They compare the DNA at the crime scene with a database in which the DNA of previous perpetrators is registered. “But not everyone who has committed a crime is in this database. After a certain period of time, the information on a person is also deleted again, ”says Thali.
Actually, a DNA trace could be used to determine the color of a person’s hair, eyes and skin with a very high degree of probability. Likewise the origin and the age. This process is called phenotyping. It is currently still banned in Switzerland.
Forensic scientists will soon be able to use the method for certain serious crimes such as murder or rape. A corresponding legal basis is currently being drawn up. “We cannot infer a single perpetrator, but we can infer a certain type,” says the institute director.
Solve unresolved cases thanks to DNA
In two unresolved cases, the investigators currently want to perform phenotyping. On the one hand in the murder in Zurich Seefeld in 2010, where a stranger stabbed a psychiatrist in her practice. In 2015, the investigators found the DNA of the alleged killer at a crime scene in Laupen BE, after a retired couple had been killed there. Also unresolved is the case of Emmen LU, where a young woman was torn from her bike and raped in 2015. She has been paralyzed since then. There would also be a DNA trace here.
Unresolved cases are very rare in Switzerland. Last year 253 homicides were recorded, tried and completed. At the end of 2020, 96.4 percent of these cases were resolved. Means: The police were able to identify at least one accused person. In the case of rape, the figure is 87.5 percent.
This is how the voice reveals a perpetrator
The University of Zurich works closely with the Forensic Institute Zurich (FOR), which implements and implements the new methods in everyday police work. One example is so-called phonetics, i.e. the identification of perpetrators based on speech analysis.
The FOR examines threatening calls, voice messages and video clips. The voice is just as unique as a fingerprint. Phoneticists take advantage of this. For example, they compare a threatening phone call to a suspect’s voice. The disadvantage here: “The suspect has to give his vote sample voluntarily. In contrast to the fingerprint, the investigators cannot force it, ”explains Jörg Arnold, scientific director of the FOR.
The researchers at the University of Zurich are now trying to reconstruct a voice based on a person’s throat. “But that’s still a long way off,” says Arnold.
In 2018, the FOR hired its first female phonetician. The department has now grown by another two employees. The reason: More and more audio files are in circulation and can be included in investigations. The voice is also suitable for assessing the characteristics of an offender. Dialect about origin, voice quality about age, choice of words about education.
No method works alone
But that’s not proof. In general, a combination of all possible methods is necessary to solve crimes – new and tried and tested. Michael Thali: “We forensic doctors deliver findings and put them into context.”
Witness testimony and fingerprints are just as relevant to the hunt for criminals as a drop of sweat or a voice test. The real crime scene is sometimes less deceptive than the virtual one. And even a robot cannot replace the forensic doctor anytime soon.
The podcast on the topic: Blick.ch/durchblick