Complex relationship DNA testing for court

Casey Randall AlphaBiolabs

By Casey Randall, Head of Genetics at AlphaBiolabs

Last reviewed: 12/09/2022

When we talk about DNA testing for legal matters, the first thought that usually comes to mind is paternity testing; a DNA relationship test most used to determine who a child’s biological father is in child maintenance or custody disputes.

But did you know that there are multiple ways that we can verify a biological relationship between family members, using DNA?

Depending on your reasoning for instructing a legal DNA test, complex relationship testing could hold the key to securing the best outcome for your client.

In this article, we discuss complex DNA relationship testing, the types of tests available, when these tests are useful for legal matters, and what you can find out from a DNA relationship test.

Table of contents
  • What is complex relationship DNA testing?
  • When is complex relationship DNA testing useful for legal matters?
  • What are the different types of DNA test for complex relationships?
  • How are samples collected for DNA relationship tests?
  • How are the results calculated for a complex DNA relationship test?
  • When will I receive the DNA test results?
  • Where can I get a complex relationship DNA test for court?

What is complex relationship DNA testing?

Complex DNA relationship tests are DNA tests (other than paternity or maternity tests), that are used to verify biological relationships between family members.

They are most often used in circumstances where performing a DNA test with the biological parents may not be possible.

Options for complex relationship DNA tests include grandparent testing, sibling testing, aunt/uncle (avuncular) testing, and Y chromosome testing.

The tests are performed in the same way as a paternity or maternity DNA test.

Cheek (buccal) swabs are used to collect a DNA sample from two or more donors. These samples are then analysed by expert geneticists at the DNA laboratory, to identify matching DNA markers (loci).

If the individuals share enough DNA markers, this indicates a biological relationship.

If they do not share enough DNA markers, this means the individuals are unlikely to be related.

When is complex relationship DNA testing useful for legal matters?

There are several instances where it may be necessary to perform a DNA relationship test on extended family members for legal purposes.

Examples include:

  • Where a parent is unavailable for paternity/maternity testing – this could be for a variety of reasons, including where the alleged mother or father has passed away. This is useful for child custody/maintenance matters, or if your client wants to change the name on a birth certificate.
  • Inheritance disputes – where an individual has passed away, a living relative might want a DNA test to prove a relationship and make a claim against the deceased person’s estate.
  • Immigration applications – where an applicant has volunteered to submit DNA evidence in support of a Visa or citizenship application, confirming a relationship between family members.

No matter what the circumstances, it is important to remember that written consent (a signature) must be given by any person aged 16 or over whose DNA sample is being submitted for testing.

For a child under the age of 16, consent must be provided by an adult with parental responsibility for the child.

What are the different types of DNA test for complex relationships?

There are several options for complex DNA relationship tests, depending on your client’s needs.

Grandparent testing

Grandparent testing enables us to verify a biological relationship between a grandparent and a grandchild and is most used in circumstances where a child’s biological mother or father is unwilling or unavailable to participate in a maternity or paternity test.

Every person inherits half of their DNA from each of their parents, meaning that a grandchild will share DNA markers with their grandparents.

This test is more likely to be conclusive if both grandparents from either the paternal or maternal side are tested, however it can also be performed with just one paternal or maternal grandparent.

Sibling testing

Sibling testing allows us to establish whether one or more siblings have the same father or mother (or both).

Full siblings usually have more DNA in common than half siblings, while half siblings normally share more DNA than unrelated persons.

When a sibling test is conducted, the laboratory will determine the genetic profiles of the alleged siblings.

Based on the genetic material shared by each sibling, a sibling DNA index or likelihood ratio is calculated to determine the most likely relationship.

Aunt/uncle (avuncular) testing

As with grandparent testing, aunt/uncle DNA testing – also known as avuncular testing – is useful when the alleged parent of the child is unable to provide a sample for a maternity or paternity test.

For these types of tests, the aunt or uncle must be a full biological sibling of the alleged mother or father, as this helps increase the likelihood of a conclusive result.

Y chromosome testing

Y chromosome testing, also known as Y-DNA testing, is a test used to determine whether male relatives are biologically related via the paternal line.

A Y-DNA test works because all male children inherit their Y chromosome from their father. Male children will pass the Y chromosome from their father onto their own male children when they become fathers.

The low mutation rate of the Y chromosome means that males coming from the same paternal line will always share the same Y chromosome.

A full match between Y chromosomes confirms that two (or more) males are related. If the males have different Y chromosome profiles, then they are not related.

How are samples collected for DNA relationship tests?

All DNA relationship tests work in the same way, by analysing the DNA samples of individuals and comparing them to identify matching DNA markers (loci).

Each person inherits half of their genetic material from each of their parents, meaning that individuals who are biologically related are likely to share more DNA markers than individuals who are unrelated.

For a court-approved complex relationship DNA test, cheek cell DNA is collected from each sample donor under strict chain of custody conditions, using buccal (cheek) swabs.

Following chain of custody procedures for sample collection ensures the samples are collected from the right people, prevents sample tampering, and ensures the DNA test results can be accepted by the courts.

Once the samples have been safely transported back to the laboratory, they can then be analysed and compared by geneticists, to determine the likelihood of the individuals being related.

How are the results calculated for a complex DNA relationship test?

Once the DNA test has been performed, expert geneticists will make a biostatistical calculation to confirm the relationship between the tested individuals.

There are three possible outcomes for complex relationship DNA test results when calculating the likelihood ratio for relatedness:

  • A score of 10+ is supportive, meaning that there is very strong evidence that a relationship does exist.
  • A score of 0-0.1 would be classed as not supportive of a relationship.
  • Any calculation falling within 0.11-9.9 would be considered

If the result is inconclusive, it means that it is not possible to determine if a biological relationship exists between tested individuals.

When will I receive the DNA test results?

At AlphaBiolabs, we appreciate the urgency involved in receiving DNA test results for legal matters.

That’s why we provide the fastest DNA test results in the industry, with next day* legal DNA tests results available as standard, and same day* legal DNA test results available if required.

We include a Statement of Witness expert report as standard within the DNA testing fee.

This enhanced report includes the likelihood ratio for relatedness based on the analysis of the DNA samples, details on the type of analysis performed, information on the chain of custody collection process, and qualifications of the reporting scientists.

Our legal DNA test results are court-approved and accepted by Family law courts, the Ministry of Justice, the Child Maintenance Service, UK Visas and Immigration and the Home Office.

*Working days from when the samples arrive at our laboratory before 10am

Where can I get a complex relationship DNA test for court?

AlphaBiolabs is a long-established, highly regarded, and UKAS-accredited laboratory, with over 15 years’ experience providing court-approved DNA testing for family law professionals, social workers, local authorities, and immigration solicitors.

Our legally-instructed DNA testing follows strict procedures to maintain chain of custody, meaning that our results are court-approved and accepted by the Family Court, the Ministry of Justice, the Child Maintenance Service, UK Visas and Immigration and the Home Office.

For expert advice on which DNA test is best for your client, call the AlphaBiolabs Legal team on 0333 600 1300 or email and a member of the team will be in touch.

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Casey Randall AlphaBiolabs

Casey Randall

Casey Randall, Head of DNA Testing at AlphaBiolabs

Casey joined the AlphaBiolabs team in 2012 and heads up the DNA laboratory.

An expert in DNA analysis and a member of the International Society for Forensic Genetics (ISFG), Casey holds an MSc with Distinction in DNA Profiling and a First-Class BSc with Honours in Forensic Science.

Casey is responsible for maintaining the highest quality testing standards, as well as looking for ways to further enhance the service that AlphaBiolabs provides and exploring new and innovative techniques in DNA analysis.

Connect with Casey on LinkedIn

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