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What is Legal DNA Testing?

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What is Legal DNA Testing

Legal DNA testing is typically used to confirm the paternity of a child when dealing with child maintenance, custody, and immigration issues. The DNA tests themselves are crucial in many legal cases, as the court-ordered results provide scientific evidence to determine disputes.

Legal DNA testing is the formal equivalent to peace of mind DNA testing which is a test that can be completed at home. Legal DNA testing is used to determine the biological relationship between two or more individuals and is court-approved.

For legal DNA tests to be valid for a case, they must be performed by an official authority that will send the DNA samples away for testing, leaving no room for contamination. For a test to be legal, the participants must never handle the blood or saliva sample themselves, as this could affect accuracy. Photos may also be taken for visual verification.


Why would a legal DNA test need to be taken?

A legal DNA test proves whether or not two parties are related, which is the primary reason behind taking the test. A common reason for taking a legal DNA test is when child maintenance or custody is involved. If there is an issue, such as one parent refusing to take a voluntary DNA test, a legal DNA test (court-approved) can be court-ordered, which can establish the biological parent.

For immigration applications, proof of a genetic relationship between two people is often required to allow the applicant to join their family in a foreign country. It is vital that this must be proven by a legal DNA test and not a peace of mind DNA test.


How accurate is a legal DNA test?

Legal DNA tests sample up to 24 genetic ‘markers’ (areas of a person’s DNA), to analyse the relationship of the individuals involved, and the two profiles are compared. If all genetic markers on the profile of the alleged parent and child are identical and match at every point, then it is confirmed that the tested individual is the biological parent of the child. If genetic markers do not match, then the tested individual is not the biological parent of the child.

With maternity and paternity DNA tests, the results will indicate a maternal or paternal relationship in excess of 99.9%. If the man or woman are not the biological parents of the child, this will be a conclusive result with 100% certainty.

Zygosity DNA Tests determine whether multiple children from the same birth (twins, triplets, quadruplets, etc.) are genetically identical or not. The results of this test are more than 99.99% conclusive.

Avuncular DNA Tests are often needed to establish a relationship with a mother or father in situations where that parent is not available to be tested. The alleged aunt or uncle of the child who would like to establish their biological relationship with the child is therefore tested instead.

The likelihood of obtaining a conclusive result when undertaking an avuncular test varies depending on which individuals are participating in the case:

A Siblingship DNA Test is not as conclusive as a paternity DNA test and can only report the most likely relationship. The likelihood of obtaining a conclusive result when undertaking a sibling test varies depending on which individuals are participating in the case. However, if either of the parents of the siblings who are being assessed are available for testing, this will aid the testing and may increase the certainty of the result.

When testing if two individuals are Full or Half Siblings:

When testing if two individuals are Half Siblings or are Unrelated:


How is a legal DNA test performed?

For paternity cases an individual requiring the test books in with a legal DNA testing facility and meets with the doctor. The test is taken, with one copy sent straight to the court to be used as evidence, and one copy sent to the named parent that lives with the child. Almost all legal DNA tests require the participants (of all ages) to take a swab from the inside of their cheek. This is known as a buccal swab and causes no harm. For prenatal paternity cases, blood is often drawn for the legal DNA sample. All court-approved legal DNA tests are required to be performed by a Ministry of Justice accredited laboratory directed by the civil courts in England and Wales under section 20 of the Family Law Reform Act 1969.


Legal DNA testing sample collection

Unlike a peace of mind test, where individuals are responsible for collecting their own samples, legal DNA testing has a very different procedure in place. Court-approved DNA tests require that an independent witness, such as a GP or health professional, oversees the sample collection process and is able to verify photo ID and maintain a chain of custody.

The chain of custody is an essential procedure used in legal scenarios whereby all samples must be collected in a certain way so that the provenance of each sample collected is documented. This maintains its admissibility as evidence in court.


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