Legal and court ordered DNA testing

A legal DNA test could refer to one of many different tests of which results conclusively prove that the people who took part in that test are biologically related. These results can also be used to disprove the alleged relationship. These tests provide legally admissible results to the parties concerned, supporting or disproving their relationship claims.

Most of the legal tests carried out are paternity tests. A legal paternity test will provide incontrovertible evidence that the tested male is the biological father of the child or children. There are many reasons why this proof of relationship would be required. In some cases, the DNA test is court ordered and carried out following the request of a judge. In other scenarios, the participants themselves decide to take the DNA test through a company or laboratory.

It is important to bear in mind that in some countries only results provided by an accredited laboratory can be accepted in court cases as evidence of a biological relationship between two or more people. The accreditations required are usually dictated by the local courts or government. In Australia, for example, the laboratory must be accredited by the National Association of Testing Authorities. In the UK, laboratories must be accredited by the Ministry of Justice for the results are to be suitable for legal or immigration cases. It is important to verify the laboratory chosen is listed on the Ministry of Justice website. Laboratories accredited by the Ministry of Justice include The Genetic Testing Laboratories. If the laboratory does not have the required accreditations, the DNA test results may be turned down when presented in court.

Generally, we can say that paternity testing is used in cases of:

• Child custody / alimony payments

• As proof of relationship for citizenship and immigration

• Changing the name on a birth certificate

Another case which sometimes crops up is that of illegitimate children. Illegitimate children are those children which have not been recognised by their parent(s) and are usually born outside marriage.

Although the term is still used, it is considered anachronistic and is slowly being replaced with "out of wedlock" or "natural child". Illegitimate children have never been legally recognised by the man who fathered them but might, following the biological father's death, wish to make a claim to the deceased's estate. This again is generally a very difficult and complex issue to solve, namely because the illegitimate child will find it very difficult to gain access to DNA samples from the alleged father and the relatives will unlikely consent to a DNA test.

Another case which from time to time appears in court is paternity fraud. Paternity fraud happens when the mother of the child has knowingly deceived a man into believing he is the father of a child. Paternity fraud may be hard to prove as the intention to deceive could be quite difficult to present as a case in a way that is convincing to a court. This said, other evidence might be brought to bear.

In cases where the siblings or alleged siblings want to prove they are born from the same father, sibling tests can help provide them with the proof they need. For example, female siblings who wish to know if they have the same dad can carry out an X chromosome test. If only males are involved, a Y chromosome test will prove conclusive and if brothers and sisters need to prove they share a common parent they can carry out a STR test (short tandem repeat test).

Sample collection

How can we ensure that the results of a DNA test used for legal purposes and that will be used in court actually shows the true results? The whole validity of any DNA test results relies on the sample collection and legal tests have a very strict sample collection procedure that is called a chain of custody.

A chain of custody documents every stage of the sample collection and a number of forms need to be filled in. All test participants must provide a valid form of identification as well as passport sized photographs. Samples for this type of test are not collected by the test participants but by an appointed professional who is known as the sampler. The sampler will need to endorse the photos by signing the back of these and declaring that "I [Samplers Name] certify that this is a true likeness of... [person's name]". The sampler then signs and dates the photos.

The sampler is not only the "sample collector" but an official witness who will collect the sample and testify to the fact that no cheating or deliberate errors have occurred in an attempt to alter the results. To conform to the chain of custody, the sampler handles the samples at every stage - no one else can handle them until they reach the laboratory. Once in the laboratory, the analysis is carried out and the published result, ready to be presented in court, must be notarised.

Sarah White specialises in the field of DNA and Genetics