Forensic Genetics Unit

1. What is a paternity test?

A DNA test is used to confirm or disprove the existence of a specified relationship between two or more people. Four steps are necessary to achieve this goal: First, a sample is taken from the persons concerned. We usually use a swab from the inside of the cheek with a cotton swab or a few drops of blood from the tip of a finger with a lancet. DNA is extracted from these samples. This DNA is amplified by PCR in order to be analysed on a capillary electrophoresis machine. The purpose of this step is to obtain genetic profiles. The genetic profiles of the persons tested are compared in order to assess the relationship between them. If necessary, the results of our analyses are evaluated by means of probability calculations. These calculations are used to determine the reliability of the results. This reliability exceeds 99.999% in most cases.

2. Why take a paternity test?

A DNA test can help you to establish with certainty a family relationship or the identity of a person. It can be useful for :

Satisfy your curiosity or remove a doubt about your own origin (reunion of brother and sister, surprising physical resemblance, etc.).
Remove a doubt about the origin of a child (paternity dispute, custody rights, access rights, adoption, etc.).
Proving family relationships for legal purposes (inheritance rights, insurance rights, rank, etc.).
Determining maternity in cases of child abandonment, abduction, maternity exchange, etc.
Confirming the origin of a child conceived through alternative reproductive technologies.
Establishing that a person has a parent in a foreign country in order to justify an immigration application or to carry out family reunification.
Resolving family disputes.

3. How to perform a paternity test?

• Regulations: Since 1 April 2007, the performance of paternity tests has been regulated by the Federal Law on Human Genetic Analysis (LAGH) and by the Ordinance on DNA Profiling in Civil and Administrative Matters (OPFI). The LAGH stipulates that in the case of private expertise, the laboratory must inform the persons concerned of the provisions of the Civil Code relating to the establishment of filiation and make them aware of the possible psychological and social repercussions of the analysis.
   
• Prerequisites: the Laboratory pays particular attention to ethics and the protection of personal data. Thus, only requests from individuals for which an informed agreement has been obtained from all adults concerned by the expertise are accepted. We do not conduct any tests without the knowledge of the persons concerned!
   
• Request: Please send us your written request or fill in, sign and return the private request form for a family relationship test.  You can also contact us by phone for information. We accept applications from all countries, but our reports are generally written in French. On request, they can be written in German or English.
   
• Acceptance of the request and appointment: we will study your request and contact you promptly to inform you of our decision. This decision is based primarily on ethical and legal criteria and on our ability to meet your request within the time and cost limits. In the event that the expertise is accepted, we will determine the modalities for the samples.
   
• Dispatch of the expert report: our report will be sent to you within 10 working days of the samples being received by the laboratory. Please note that we will only start the analyses after we have received your payment.

4. Is it possible to request a private paternity assessment?

Yes, provided that the persons concerned give their written consent.

5. Is it possible to request an analysis of biological traces (sperm, hair, etc.) in private?

No, these analyses are only carried out at the request of a judicial authority.

6. I want to carry out a private paternity search. What do I have to do?

Simply contact our center by telephone 021 314 38 64, by e-mail (test.adn@chuv.ch), by post or by returning the completed and signed private request for a parentage test form, so that we can assess the feasibility of the requested test and give you the necessary information.

7. Do I need the mother's consent to carry out a paternity test?

Yes, when the child is a minor, it is imperative that both parents give their consent. When the child is 16 years or older, he/she can carry out the test with only one of his/her parents without the agreement of the other parent.

8. What biological material should be taken for a paternity test?

This kind of test can be done with saliva samples taken with a cotton swab, or with a few drops of blood taken from a fingertip.

9. Where do I go to take the samples?

Samples can be taken by appointment only at our Center (Chemin de la Vulliette 4, CH-1000 Lausanne 25), at the HUG (Geneva) and at the Institut Central des Hôpitaux Valaisans (Av. du Grand-Champsec 86; 1951 Sion). It is also possible, especially for people living abroad, that samples are taken by another doctor (or laboratory). In such a case, it is essential that we contact him/her to explain the sampling procedure and send him/her the necessary material.

10. What is the price of a paternity expertise?

Please refer to the price table in force.

11. How long does a paternity test take?

For standard parentage tests, the DNA analysis report is sent within ten working days after the samples have been received by the laboratory.

12. How reliable are the DNA analyses performed by our unit?

Each forensic examination performed at our Center complies with the Federal Law on Human Genetic Analysis and the Federal Law on the Use of DNA Profiles in Criminal Proceedings and on the Identification of Unknown or Missing Persons. The Forensic DNA Unit is accredited according to ISO 17025 (SAS; No. STS 0420) and approved by the Federal Office of Police. The Forensic DNA Unit has been performing paternity tests since the 1950s and participates in several Swiss and international quality controls each year. All tests are confirmed by a second independent analysis. WMU test results are reliable

13. Can DNA results be used in court?

Yes, the results of a forensic examination performed at the Forensic DNA Unit can be presented in court.

14. Are the DNA results confidential?

No. Personal data and the results of the analysis are strictly confidential and will only be communicated to the person or official body that requested the analysis. All CURML staff are bound by medical and official confidentiality.

15. What is a DNA paternity test?

Paternity testing is based on the principle that each child receives half of its genetic material (DNA) from its mother and the other half from its father. By comparing the DNA profiles of the child and the mother, it is possible to determine, for each autosomal marker analysed, which genetic trait is potentially of maternal origin; this is the genetic trait common to both individuals. The second genetic trait present at the same marker must be from the child's biological father. When the DNA profile of the alleged father is compatible with that of the child, the value of this compatibility is determined and a probability of paternity can be assigned. With current techniques, we generally obtain probabilities of over 99.999%. When incompatibilities are found at five or more markers, the alleged father is not considered to be the biological father of the child. Single parent tests are only accepted if the child is of age and can give informed consent or when it is not possible to sample the other parent. Other kinship tests may be offered (sibling tests, maternity tests, twin tests, cousin tests, grandparent tests, etc.). Before accepting a request of this type, however, we must assess its feasibility and have the agreement of all the people involved in the analyses. An estimate is provided to you according to the analyses to be carried out.

16. What are the advantages of DNA paternity testing?

The speed and reliability of the analysis.
As the probability of paternity is generally higher than 99.99% in the case of non-exclusion of the alleged father, it can be said that paternity is practically proven. DNA analysis can also be used to resolve more complex situations, such as when the presumed father is deceased. In this case, the expertise is carried out with either the paternal grandparents or the brothers and sisters of the deceased or with other children from another union.

Glossary

DNA

DNA (deoxyribonucleic acid) is the medium of heredity. It is made up of four bases (adenine, thymine, guanine and cytosine) which combine to form a double helix. This double helix is found compacted in the form of chromosomes in the nucleus of our body's cells. The human species has 23 pairs of chromosomes.

PCR

PCR is a polymerase chain reaction in which an enzyme, Taq polymerase, copies a target fragment of DNA a large number of times. The specificity of this amplification is determined by the choice of a pair of primers (short DNA sequences) that are complementary to the sequences on either side of the target fragment. PCR can synthesise millions of copies from a single starting DNA fragment. These copies can be analysed by capillary electrophoresis.

Capillary electrophoresis

The separation and detection of the amplified DNA is done by capillary electrophoresis equipment. The DNA previously amplified by PCR is injected into micro-tubes (capillaries) filled with a viscous liquid (polymer) which will allow the different DNA fragments to be separated under the influence of an electric field. The size of the fragments is determined by their migration speed. The size of the DNA fragments is determined by the speed of their migration, which is used to identify the genetic characteristics (alleles).

Genetic profile

A genetic profile (or DNA profile) consists of several genetic markers (synonym: system, locus, microsatellite or STR). These correspond to portions of DNA that are variable and whose analysis makes it possible to characterise individuals.

In an individual, one or two traits (synonym: alleles) can be found for each genetic marker. If the individual has inherited the same trait from both mother and father, only one trait will be visible; the individual is said to be homozygous for that marker. If the individual has inherited different traits from his parents, two distinct alleles will be visible on the genetic profile. The individual is in this case heterozygous for the marker.

All traits that may be present for a genetic marker are numbered. The results are therefore of the type 16 (or 16-16) for a homozygous locus (i.e. the individual has two copies of the allele number 16 at this locus) or 15-18 for a heterozygous locus (i.e. the individual has one copy of the allele number 15 and one copy of the allele number 18 at this locus)

The genetic markers used by the Laboratory are located in non-coding regions of the DNA. In other words, these markers do not provide information on physical characteristics of individuals (eye colour, height, predisposition to diseases, etc.). The Laboratory has a range of markers. It generally uses the commercial kits PowerPlex Fusion 6C, PowerPlex-Y23, NGM SElect, Argus X12-QS and mitochondrial markers.

Probability calculations

The probability calculations used for genetic testing are based on a measure of the relative credibility of two alternative hypotheses. For a classical paternity test, these hypotheses are generally as follows:

Hypothesis 1 (H1): the alleged father is the biological father of the child

Hypothesis 2 (H2): The alleged father is not the biological father of the child. In this case a man not related to the alleged father is the biological father of the child.

To make the calculation it is necessary to know the population frequencies of the alleles of the genetic markers used. This makes it possible to calculate the chances that two randomly selected individuals have common alleles but are not related. The likelihood ratio (LR) that we calculate makes it possible to estimate which hypothesis, of H1 or H2, is more likely. If, for example, we obtain an LR of 1’000, this means that it is 1’000 times more likely to observe the genetic profiles obtained if the presumed father is the biological father (H1) rather than another unrelated person (H2).

In our expert reports, the LR is directly transformed into a probability of paternity. This calculation implies several assumptions. In particular, it assumes that the a priori probability is 0.5. In other words, before the tests, the presumed father has a one in two chance of being the biological father. In such a case, the probability of paternity is LR/(LR+1). For the above example, it would be 99.9% (=1'000/1'001). According to Swiss jurisprudence, a probability of more than 99.8% allows the tested relationship to be considered "practically proven".

Sample collection

The majority of DNA tests performed at the Laboratory are performed using saliva or blood deposited on blotting paper (FTA®). This type of sample is ideal, as it is easy to store and there are no precautions to take before the test (no need to come on an empty stomach, refrain from smoking, etc.). Please note: only samples taken at our institute have a guaranteed identity.

It is possible, especially for people living abroad, that the blood samples are taken by another doctor (or laboratory). In this case, we accept no responsibility for the authenticity of the samples. If another service is involved in the blood test, it is essential that we have contact with them. It may be possible, under very specific conditions (disappearance, death, etc.), to carry out a DNA test using other types of samples. Please contact us for further information on this point.

Guaranteed Identity

Laboratory staff follow strict guidelines when collecting samples to ensure that they have a guaranteed identity. This is essential when results are to be presented in court. The following means are used to ensure the identity of samples: Identification: Persons over 18 years of age are requested to present themselves with a recent photo ID (driving licence, passport, etc.). This document will be scanned and included in the report. This photo will be included in the expertise report. The identification documents are completed by the laboratory staff and signed by the adults present. The information obtained is archived in our secure premises. This information is strictly confidential.