On 17 December 2021, the Swiss parliament approved an amendment to the DNA Profiles Act, allowing the extraction of additional characteristics from a DNA sample: in future, law enforcement services will be able to identify not just a person’s gender, but also other features such as their eye and hair colour. This will provide them with a new investigative tool for solving serious crime such as rape and murder and therefore allow them to target their investigations more effectively.
The revised DNA Profiles Act is scheduled to come into force in summer 2023.
Science has made enormous progress in recent years. Phenotyping now makes it possible to determine additional characteristics from a DNA sample:
Blue and dark-brown eyes can be predicted with 90-95% accuracy. Intermediate colours (such as green or grey) are more difficult to determine.
Red, blond, chestnut and black hair can be predicted with a high degree of reliability: about 69% for blond, 78% for chestnut, 80% for red and 87% for black hair. However, phenotyping must take account of certain changes in the aging process: for example, during adolescence blond hair may turn dark blond or chestnut.
Predictions for white or black skin are very reliable: 95% for black and 98% for white skin. Test reliability for intermediate skin colour is less accurate, at 84%.
Specific DNA characteristics can show with a very high degree of accuracy whether a person is from Europe, Africa, East Asia, South Asia, South-West Asia or an indigenous population in the Oceania region or the Americas.
A DNA analysis can define the age of the subject to within 4–5 years for the 20–60 age group. For younger or older people, mean deviation is higher.
The above five characteristics (eye, hair and skin colour, biogeographic ancestry and age) are also useful when combined. For example, if a DNA analysis indicates that the person is over 70 years of age, they may also have white or grey hair.
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Sometimes CODIS does not provide a match between DNA samples from a crime scene and those already in the database. When this happens, law enforcement services can carry out a familial search. This means they look in the database for a similar DNA profile indicating a close relative.
Based on the rulings of the Federal Criminal Court, the Federal Council now wants to enshrine familial searching in law. It will only be permitted for investigating crime and must be based on an order from the public prosecutor's office.
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The Legal Affairs Committee of the National Council asked the Federal Council in a postulate to examine the current regulations on deleting DNA profiles from the CODIS database. An analysis by the Federal Council concluded that the existing regulations are complex, administratively inefficient and prone to error. For example, the current retention period depends on the length of the person’s criminal sentence; if this changes or if they commit a further crime, the retention period must be adjusted accordingly. In future, this process will be simplified: the retention period will be determined in the verdict and will not change thereafter.
The new regulation is based on the principle of proportionality and on a careful weighing of the interests of law enforcement against those of the person concerned. In future, DNA profiles will only be kept for as long as necessary for criminal prosecution.
Narrowing the scope of investigations
The rape and murder of 16-year-old Marianne Vaatstra in 1999 in the Netherlands illustrates the practical use of phenotyping. Initial suspicion fell on the residents of a nearby asylum home. However, the results of mass DNA testing in the area around the crime scene were inconclusive. Law enforcement services therefore decided to use phenotyping for the first time ever on traces of blood and semen collected at the crime scene. The results of the analysis indicated that the perpetrator was a West European. This subsequently narrowed down the investigations, and the perpetrator was ultimately identified and arrested.
Obtaining clues to possible motive
In another case, involving an attempted arson attack on a mosque, the perpetrator left behind a glove at the crime scene. Although DNA found on the inside of the glove did not turn up a match, phenotyping indicated the perpetrator was probably a European man with blond hair and blue eyes. The information provided the police with an important clue, namely that the crime could have been racially motivated.
Narrowing down the number of suspects
Following a sexual assault in a small village in the Netherlands, phenotyping revealed that the perpetrator was most likely of Asian origin. This piece of information narrowed down the circle of possible suspects considerably: only one person in the village – adopted by a Dutch couple – had such biogeographic ancestry. His DNA was ultimately found to match the profile generated from traces of semen found at the crime scene.
Assessing victim and witness statements
A match between two DNA profiles generated from traces of semen found at different crime scenes revealed that two sexual assaults had been committed by the same person. One victim described her assailant as being from West Africa, while the other victim believed he was Indian. Phenotyping indicated that the culprit was, indeed, most likely of Indian origin.
A case of rape in France
The case involving Élodie Kulik is a typical example of a familial search using phenotyping.
The 24-year-old woman was raped and killed in 2002 in northern France. The offence was committed at night in a remote rural area and there were no witnesses. Based on the DNA profile generated from semen recovered from the crime scene, a large-scale investigation was carried out in the area near where the crime had taken place. A comparison between the DNA profile and several thousand others in French and other European databases was inconclusive. The French police therefore decided, for the first time ever, to conduct a familial search, which turned up a match with a man whose family lived not far from the scene of the crime. Using conventional investigation methods, including information from official registers, the police were able to trace the man's family tree and found that he had two sons. One of the sons was ruled out because of his young age at the time of the offence. The other, older son had died shortly after the offence, which was why the extensive investigation had been unsuccessful. When his body was exhumed, the profile was found to match his DNA. Thus, nine years after the crime, the police were able to identify the culprit.
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Last modification 15.05.2023