How to determine paternity without a DNA test

Liz Wood, Alphabiolabs

By Liz Wood, Health Testing Specialist at at AlphaBiolabs
Last reviewed: 12/06/2024

In this article, we look at some of the ways people try to determine paternity without a DNA test – and why DNA testing is the only 100% accurate, reliable way of establishing paternity.

Is it possible to verify paternity without a DNA test?

DNA profiling has been available for over 40 years, thanks to techniques developed by Sir Alec Jeffreys in 1984 and, by 1988, DNA fingerprinting was available for paternity testing (Adams, 2008).

However, before the availability of modern-day DNA testing, people would look at different traits, such as blood type, physical resemblance, and behaviour to determine the paternity of a child.

Let’s look at some of the ways people have tried to determine paternity without a DNA test, and why these methods are not reliable.

Blood type analysis

Before modern-day DNA tests, it was thought that paternity could be verified by comparing the blood type of the child with that of the alleged father.  

In 1900, while trying to establish why blood transfusions work in some instances and are fatal in others, scientist Karl Landsteiner discovered that human beings have ABO blood groups.

In 1910, scientists von Dungern and Hirschfeld discovered that the ABO blood group system was inherited in a Mendelian pattern. In simple terms, this means that you inherit a blood type allele from your mother and a blood type allele from your father.

However, even though we inherit our blood type from our parents, this is not a reliable way to determine paternity, as many people who are not related also have the same blood type. This means it is impossible to ascertain the true biological father of a child by comparing blood types alone.

The only way to determine paternity with 100% accuracy is via paternity DNA testing.

Inherited traits

Some people may look to verify paternity by comparing the inherited traits of a child with that of the alleged father.

When we talk about inheritance in biology, we mean genetic traits that are ‘passed down’ from parent to child. Characteristics such as eye colour, vision problems, and even genetic conditions are inherited from our parents.

The problem with attempting to verify paternity by comparing such traits is that they are complex and therefore not at all reliable for confirming paternity.  

For example, although it was previously assumed that inheriting eye colour was as simple as inheriting your blood group, there are roughly 16 different genes associated with the determination of eye colour.

Therefore, it is not possible to determine paternity by comparing the eye colour of the alleged father with that of the child.

Vision problems such as myopia, hyperopia, glaucoma, and colour blindness can be inherited, but much like eye colour, there are many different genes involved. Just because one or both parents have a particular vision problem does not mean their children will develop the same condition.

Furthermore, environmental factors such as overexposure to UV rays from the sun can also cause eye problems (e.g. macular degeneration and cancer).  

Hereditary conditions are genetic disorders that run in families and can be single-gene disorders or complex, involving multiple genes.

If a genetic condition appears in a child when no one else in the family appears to have it, or if a condition is not present in a child when many people in the family have it, it might raise questions in people’s minds about the child’s paternity.

However, without knowing which genes are involved and who is affected or unaffected, it is not possible to accurately determine paternity, without the use of a DNA test.

Physical attributes such as the ability to lose/gain weight easily and hair loss, can also be inherited.

However, these are also not accurate ways of determining paternity. Environmental factors play a big role in a person’s ability to lose or gain weight i.e. you are more likely to gain weight if you eat too much and do not exercise enough (even if your parents are thin), and you are more likely to lose weight if you eat less and exercise more (even if your parents are overweight).

In terms of hair loss, it is a myth that only one gene is responsible for balding, and your likelihood of going bald is influenced by multiple genes. So, just because a parent is bald, it does not mean that their child will be bald in the future; therefore, making this comparison cannot be used to determine paternity.

Behavioural traits/personal preferences

Much like our ability to lose or gain weight, genetics can impact our behavioural traits or personal preferences to a degree.

For example, multiple people in the same family might be musically or artistically gifted. However, this does not mean that anyone in the family who does not share this talent is not biologically related.

Our environment plays a big part in shaping who we are, what we are interested in, our talents etc.  

The genetic and environmental factors that influence our behaviours are vast and complex, and it is therefore not possible to determine paternity by simply comparing the behavioural traits of the alleged father with that of the child.

Physical resemblance

We expect to share some physical characteristics with our parents, whether it’s the shape of our nose, texture of our hair or the colour of our skin. 

However, just because a child does not look like the alleged father does not necessarily mean that he is not the biological father of the child.

The genetics responsible for our physical characteristics are incredibly complex. For example, there are more than 100 genes involved in making skin colour alone!

Skin colour is also impacted by our environment; excessive exposure to UV rays from the sun causes damage to the skin, and the body responds by making more melanin, a natural pigment that makes our skin darker.

A new-born baby has not been exposed to the sun, meaning their skin colour may appear lighter than that of their parents.

All these factors mean that it is not possible to determine paternity by comparing the physical characteristics of the alleged father and the child.

What are the limitations of trying to confirm paternity without a DNA test?

The only 100% accurate and reliable way of verifying paternity is to analyse and compare the DNA samples of the alleged father with that of the child, to identify matching DNA markers (loci).

Other ‘methods’ of determining paternity such as blood type analysis or comparing the shared physical/behavioural/inherited traits are simply not reliable for establishing paternity, for a variety of reasons:

  • Blood groups are shared by many individuals who are not related, making confirmation of paternity via blood group analysis virtually impossible.
  • Physical and behavioural characteristics such as hair colour, eye colour, body shape, and natural talents are polygenic (controlled by multiple genes), and therefore cannot be attributed to the biological father alone.
  • Environmental factors such as where, how and by whom we were raised can impact personal preferences and behaviours, meaning that the child may not share any of these characteristics with their biological father due to different upbringings/lifestyles.

Additionally, DNA testing is the only method of determining paternity that is accepted by courts, provided the laboratory performing the testing is accredited.

At AlphaBiolabs, we provide paternity testing to suit a variety of needs, including for peace of mind and for legal matters (e.g. child welfare/custody disputes, changing a birth certificate etc.), direct from our award-winning, ISO 17025-accredited laboratory.

Why is it important to confirm paternity?

Because fathers usually play an important role in their child’s wellbeing and development, establishing a father-child bond early on has many benefits.

In situations where a man is uncertain whether he is the biological father of a child, he may be reluctant to spend time with them or contribute to their upbringing.

This can damage the chances of a positive parent-child relationship and cause emotional distress both to the potential father and to the child.

This is where paternity testing is useful, providing a 100% accurate, reliable way of determining paternity, and helping to ensure that the relationship between father and child gets off to the best possible start where the man is confirmed as the biological father.

There are many other good reasons why a person might want to find out who their biological father is, that have nothing to do with building a relationship between father and child.

These include:

  • Where it is important for a person to know their full medical history – including their family history of certain diseases or health problems. This can be useful for couples/individuals trying to conceive, or for people who are simply curious about their health and want to ensure any hereditary illnesses are diagnosed and treated as early as possible.
  • Developing a sense of identity – some psychologists believe that knowing your biological background is important in helping to establish a sense of identity.

How does a paternity test work?

For a peace of mind at-home paternity test, cheek (buccal) swabs are used to collect cheek cell DNA from the alleged father(s) and the child.

These samples are then analysed and compared in the laboratory, to identify matching DNA markers (loci). Every person inherits half of their DNA from each of their biological parents, so such a comparison can help us to establish the probability of paternity.

If the tested man is the biological father, the man and the child will share DNA at every tested marker. If the tested man is not the biological father, this will not be the case.

An AlphaBiolabs paternity DNA test looks at up to 45 DNA markers (loci) – double the industry standard for DNA testing – for a 100% accurate and reliable result.

Why should I use DNA testing to determine paternity?

DNA testing is the only 100% accurate, reliable way of establishing paternity, making it the go-to method for anyone with questions surrounding a child’s true paternity.

There are many circumstances in which a paternity test might be needed and, thanks to accredited laboratories like AlphaBiolabs, it is now easier than ever to order a paternity test online and get the answers you need.

Examples of who might need a paternity test include:

  • Mothers who are unsure as to who their child’s biological father is after a baby has been born
  • Men who have doubts about whether they are the biological father of a child
  • Expectant parents who want to verify paternity before the baby is born – this can be done through a completely safe and risk-free non-invasive prenatal paternity testwhile the mother is still pregnant
  • Grown-up children who have questions about their parentage, and want a paternity test to confirm that the man they believe to be their father is actually their biological father
  • Men who are being asked to provide child support for a child they did not previously know existed, where there is doubt about paternity
  • Siblings who want to know whether they share the same biological father
  • Children who have been adopted or conceived via a sperm donor, who want to find out who their biological father is
  • Individuals who wish to make a claim of inheritance after their father has passed away, where paternity is in dispute

Please note, if you require a paternity test for use in legal matters, such as changing the name on a birth certificate, for child maintenance, for custody disputes, or for wills and probate, you will need to instruct us for a legal DNA test.

Unlike a peace of mind, at-home paternity test, where you can collect the DNA samples yourself, a legal paternity test requires samples be collected by a professional sample collector under chain of custody conditions, to ensure the results of the test are court-admissible.

Call our friendly and knowledgeable Customer Services team on 01 402 9466 or email to arrange your sample collection and court-approved paternity test.

Where can I get a paternity test?

AlphaBiolabs excels in offering fast, accurate, and reliable paternity testing using cheek (buccal) swabs – the industry-wide gold standard for relationship DNA testing,

Our DNA Paternity Test is the fastest and most popular DNA paternity test in Ireland, analysing up to 45 DNA markers for a 100% accurate result.

You can order an AlphaBiolabs Paternity Test online now, direct from our accredited laboratory, to receive results in 2-3 days.*

Got questions about our paternity testing? Call our friendly and discreet Customer Services team on 01 402 9466 or email to discuss your requirements.

*From receipt of samples into our laboratory, before 10am.

Order your home paternity test

Buy an AlphaBiolabs Paternity Test online now from just €119

Liz Wood, AlphaBiolabs

Liz Wood

Health Testing Specialist at at AlphaBiolabs

Liz joined AlphaBiolabs in 2021, where she holds the role of Health Testing Specialist.

As well as overseeing a range of health tests, she is also the lead on several validation projects for the company’s latest health test offerings.

During her time at AlphaBiolabs, Liz has played an active role in the validation of the company’s Genetic Lactose Intolerance Test and Genetic Coeliac Disease Test.

An advocate for preventative healthcare, Liz’s main scientific interests centre around human disease and reproductive health. Her qualifications include a BSc in Biology and an MSc in Biology of Health and Disease.