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In the hope of avoiding identification, criminals often wear gloves so that they do not leave fingerprints at the scene of the crime. However, the police can recover another type of evidence at the scene of a crime that allows them to clearly identify the perpetrators: deoxyribonucleic acid, better known as DNA. DNA is crucial in criminal investigations, as it contains genetic information that is unique to each person – the only exception being identical twins, who have exactly the same DNA.
DNA evidence recovered from a crime scene is sent to one of the seven DNA analysis laboratories in Switzerland, which are equipped with state-of-the-art technology. The laboratory then extracts a DNA profile from the material.
There are two types of DNA profile:
- Personal DNA profile: generated using DNA taken directly from suspects, victims or deceased persons – often through a cheek swab.
- Crime scene DNA profile: generated using DNA that has been extracted from evidence found at the scene of the crime – hair, skin cells, semen or blood, for example.
DNA profiles may only be created on the orders of a public prosecutor or a court when investigating a felony (e.g. a murder) or misdemeanour (e.g. an assault). Outside of criminal proceedings, DNA profiles can be used to identify missing, unidentified or deceased people.
The Swiss Combined DNA Index System database (CODIS) contains both personal and crime scene DNA profiles. When new DNA profiles are created, they are also compared with the DNA profiles already available in CODIS. There can be three types of match:
- Crime scene evidence matches a person: Trace DNA found at a crime scene matches the profile of a person registered in the database. This gives the police the opportunity to question the person and make progress with the case.
- A person matches crime scene evidence: When the DNA profile of a person is entered into CODIS for the first time, it is found to match a crime scene DNA profile stored in the database. This allows even cold cases to be solved.
- Crime scene evidence matches other crime scene evidence: Even if no connection can be established between a crime scene DNA profile and that of a person registered in the database, the search does not have to end there, as matching DNA profiles can also be found at different crime scenes. The perpetrator may remain (as yet) unknown, but this type of match proves that they have been active at multiple crime scenes. These matches can often bring to light previously unrecognised connections between unsolved crimes.
The rules for handling DNA profiles and the DNA database are laid down in law. Protecting personal privacy has top priority throughout the entire process – from sampling to analysis, comparison in the database and deletion. For example, direct access to CODIS is granted exclusively to the DNA database central coordination unit that the University of Zurich Institute of Forensic Medicine operates on behalf of fedpol. The associated personal or case details are stored separately from the DNA profiles in another database. Only fedpol is authorised to establish the link between DNA and personal data.
In cases where a DNA profile does not match a sample in the DNA database, phenotyping can be used to generate additional information in support of an investigation. This process, first introduced on 1 August 2023, uses DNA samples to obtain information about a person's physical appearance, for example eye, hair and skin colour, biogeographical ancestry and approximate age. Searching the DNA database for DNA profiles similar to the crime scene profile can be helpful, as this similarity among DNA profiles could indicate possible family relationships.
Phenotyping and familial searching are used only in cases involving serious crimes, such as murder or rape.
Here too, criminal justice and forensic science agencies work together closely – every new DNA profile can be the one that provides the decisive lead in solving a crime. Introduced in 2000, the national DNA database is now an integral part of the fight against crime, both nationally and internationally.
Last modification 04.03.2025
