DNA analysis

Use of DNA analysis today

Analysing DNA has been part of everyday practice in law enforcement for many years. To compile a profile, a DNA sample is required. This can come from one of two sources:

  • directly from a person (i.e. a suspect, victim or deceased person) for example by means of a buccal swab; 
  • from traces (e.g. hair, skin, blood, sperm, saliva) left behind at the scene of a crime.

DNA profiles are stored in the national CODIS database. A DNA sample taken from the scene of a crime can be compared with profiles already in the database. If the comparison yields a match, or a ‘hit’, this can mean:

  • a match has been found between a sample from a crime scene and a sample in the database from an unidentified person (sample-sample match); 
  • a match has been found between a sample from a crime scene and a sample in the database that can be attributed to a specific person (sample-person match). The police can then question that person to find out what role they play in the case under investigation.

A DNA profile may only be compiled as part of a criminal investigation or to identify missing or deceased persons. Moreover, it requires authorisation by a public prosecution service or a court.

A DNA profile may only be used to determine the gender of a person. This is the only outward feature law enforcement is permitted to extract from a profile.

An operation co-ordinated by Europol identifies numerous people throughout Europe who are viewing and passing on child pornography. It includes Swiss nationals in 14 cantons.

The fedpol investigator who analyses the data becomes suspicious during a chat. The manner in which one man is expressing himself makes the investigator suspect that his activities are not limited to just chatting, but that he has already met up with several children. The man in question is not known to the police up to this point.

The investigator notifies the cantonal police of her suspicion. The police order a DNA sample to be taken from the man for analysis. The result confirms the investigator’s suspicion: the man’s DNA matches a profile from an unsolved case from ten years previously involving the rape of a minor. Additional investigations uncover eleven further sexual offences, including six connections to minors and two cases of sexual assault on minors. The DNA profile of the man also matches samples taken from a case involving a rape and two further cases of sexual assault on adults.
 

In December 2008, two young men break into the villa of an elderly couple near Lausanne. The two men are caught off guard by the owner of the house and his wife, and subsequently beat the elderly man to the ground while his wife looks on, helpless. The man suffers severe injuries and dies a short time later at the crime scene.

The police find a single coat button at the scene. The DNA extracted from it matches a profile in the CODIS database belonging to a man who was arrested several years before for theft and burglary. Thanks to the hit in the database, investigators ultimately identify and arrest both culprits.

In 2011, two men attack a watch and jewellery shop in Basel. One of the attackers is armed and threatens the staff, while his accomplice ties them up. The attackers get away with jewellery and watches worth several tens of thousands of francs. Although the hunt for the attackers is underway immediately, they are able to flee.

In 2014, two people attack an 85-year old pensioner in an apartment block also in Basel. The victim, who becomes unconscious at times, is tied up and suffers various injuries. The culprits steal money and are able to flee unnoticed.

An analysis of DNA found at both crime scenes reveals that the same people are involved in both attacks. The police finally arrest the attackers in 2015 when, during a third break-in, one of them is caught. His DNA profile is run against the DNA database and matches the DNA traces found at the scene of the first two crimes, therefore linking him to the attacks. Further investigations ultimately lead to the arrest of his accomplice.

Legal basis

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