Can a paternity test be wrong?

Liz Wood AlphaBiolabs

By Liz Wood, Health Testing Specialist at at AlphaBiolabs
Last reviewed: 07/12/2023

Doubting the paternity of a child can be a worrying time. Whether you’re a father questioning your relationship to your child, or a child looking to find out who your father is, the process of determining paternity can be confusing and stressful.

A good laboratory, such as AlphaBiolabs, will make every effort to ensure that the DNA testing process is as easy as possible and provides you with the answers that you need.

In this article, we discuss paternity tests; what they are, how they work, and if paternity tests can ever be wrong.

What is a paternity test?

A paternity test is used to establish who is, or is not, the biological father of a child.

The method used to establish paternity has changed drastically over the past 100 years. What was once a relatively unreliable blood typing test, is now an extremely reliable and accurate cheek swab DNA test.

In a paternity test, the father in question – the potential father – and the child both provide a cheek swab sample. The samples are tested to see if they share specific DNA markers.

We inherit 50% of our DNA from our biological mother, and the other 50% from our biological father. This means that 50% of the DNA markers identified in the child’s sample should match the identified DNA markers in the biological father’s sample.

How does a paternity test work?

Doing a paternity test with AlphaBiolabs is quick and easy.

After collecting your simple and painless cheek swab samples and posting them back to our laboratory, we extract the DNA from the swabs.

The extracted DNA is then amplified by a process called polymerase chain reaction (PCR). PCR makes lots of copies of the original DNA. This allows us to analyse the DNA in greater detail.

After PCR, the sample goes through short tandem repeats (STR) analysis using a Genetic Analyser. This process separates the DNA fragments by size and STR marker, and produces a DNA profile of the sample donor.

STRs are short repeated sequences of DNA (about 1-6 base pairs in length). STRs are found throughout the genome, mostly in non-coding regions. A non-coding region refers to part of your DNA that doesn’t code for amino acids – the building blocks of proteins.

STRs are highly variable between unrelated individuals. STR analysis is therefore very useful for identification or relationship testing purposes.

Following STR analysis, the DNA profiles are used to perform the paternity relationship analysis. This is done by comparing the profiles and considering the probability that the two sample donors are related as father and child.

Paternity can be established in this way because of how we inherit DNA. We inherit 50% of our DNA from our biological mother and the other 50% from our biological father.

The DNA markers used in our relationship DNA testing exhibit the highest possible variation to discriminate between samples, which helps achieve a conclusive result.

To read more about how our paternity or other relationship testing works, visit our DNA learning centre. You’ll find lots of articles there, including the history of DNA testing and the science behind it.

Can a paternity test be wrong?

As an ISO 17025 accredited laboratory, AlphaBiolabs adheres to the strictest standards and protocols to ensure that the result you are given is accurate. A probability of paternity that is > 99.99% confirms the biological relationship between the father and child.

However, for peace of mind paternity testing, the results that we obtain rely on the correct samples being submitted, and on the information provided by the sample donors.

Paternity fraud

Paternity fraud is the act of intentionally misidentifying the father of the child, when there is knowledge or suspicion that he is not the biological father.

In practice, this might be achieved if someone swaps the swab of the potential father in the test with a swab of the biological father without informing the testing laboratory or the potential father.

Conversely, someone may swap the swab of the potential father with someone who is not related to the child in order to obtain a false exclusion result.

Someone may also attempt to cheat the test by swapping the potential father’s swab with someone related to the child. Laboratories can detect this easily, as there will be too many DNA mismatches between the child and potential father.

If the mother of the child submits a swab from herself, pretending to be the potential father, then no Y chromosome markers will be present in the sample, and so no result will be given.

DNA mutations

A mutation is a change in the sequence of DNA. DNA mutations can either be inherited (passed on from one generation to the next) or acquired (develops at some point in a person’s life, not inherited).

There are several different types of mutations, such as a deletion or insertion of one or more nucleotide bases.

Mutations most commonly happen during cell division. Our cells divide and form new cells when we grow or if we need to replenish cells due to cell damage.

To do this, our body makes a copy of our DNA for the new cell. Sometimes a mistake is made during this process, and a mutation occurs. Usually mutations, especially in non-coding regions of DNA, aren’t harmful, and our bodies are actually very good at repairing these mistakes.

However, sometimes these mutations aren’t repaired, and the change is passed on to other cells during cell division. If the mutation is present in germ cells (sperm and egg cells), the mutation can be passed on to the offspring.

If a mutation occurs within an STR, it might cause a mismatch between the DNA of the child and the parent(s).

STRs are highly variable between unrelated individuals, which makes them ideal for identification or relationship testing purposes. However, they have a higher mutation rate than other parts of your DNA.

We should normally observe a 50% match in the DNA between a child and biological father. If we suspect a mutation has occurred resulting in a mismatch between the potential father and child, we will assess the likelihood of a mutation occurring. We then factor this into our probability of paternity from the samples provided.

Laboratory errors

AlphaBiolabs is accredited to ISO 17025 and ISO 9001 standards. This means that we conduct all of our work to the very highest standards. We are subjected to yearly scientific auditing, which ensures that we continue to provide the best service to all of our customers.

We follow strict procedures that ensure all of our samples are handled correctly. Samples, data, and results are all multiple-checked by highly-trained scientists to ensure that all of our relationship testing results are correct.

We won’t release results to you if your samples have not met our acceptance criteria. If we can’t obtain a DNA profile from the swabs provided by the sample donors, we will send you a new kit so that you can recollect your samples, free of charge.

If we can’t confirm or rule out a paternal relationship (i.e. the result is inconclusive), we will ask you to provide a sample from the biological mother if possible, to help us obtain a conclusive result.

Our peace of mind paternity DNA test is 100% accurate based on the samples and information provided by you. However, the results are not admissible in court.

If you require a paternity test result that can be used in a court of law, visit our legal  DNA testing page. Our legal DNA paternity test involves strict chain-of-custody sample collection conditions, and the results can be used in legal cases.

Where can I get a paternity test?

You can order a peace of mind paternity test or legal paternity test online now with results in just 2-3 days.

If you have any questions about the test or require further assistance, call our friendly, knowledgeable Customer Services team on 0140 29466 or email

Home Paternity Testing Kits

Order your Paternity Test online now for 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.

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