OCTOBER 21, 2021

Can a Paternity Test be “Wrong?”

So many important decisions rest on DNA results, and it’s normal to feel on edge while you wait for them. When a report is issued but the answer isn’t what someone expected or hoped for, the same question tends to follow: Can a paternity test be wrong?

The lab science behind paternity testing is extremely reliable, but a result is only as good as the samples and information behind it. A DNA test can be wrong, but the problems almost always trace back to what was submitted to the lab rather than the analysis itself. Here’s where those problems come from and how to avoid them.

When Paternity Fraud or Father-Identification Mistakes Happen

Mistaken paternity is more common than many people assume, at least among cases that reach a lab. AABB, the organization that accredits relationship testing labs, collects case data from accredited labs and publishes it in its relationship testing technical reports. Those reports have consistently shown that a meaningful share of the men tested are excluded as the biological father. That reflects people who already had a reason to test, not the general population. Some of those cases involve deliberate paternity fraud, while many come down to an honest mistake about who the father is.

What Does Paternity Fraud Look Like?

Here are some ways at-home (non-legal) paternity-test results can be manipulated so that they don’t indicate the correct biological father:

• The mother can submit the DNA for a known child of the possible father as the DNA of the child in question in order to get a positive result
• The possible father submits his buddy’s DNA as his own in order to get a negative result
• After DNA is collected from the right people, the mother or possible father tampers with the mailing envelopes and submits DNA for different people

Can’t the Lab Catch Fraud?

In some cases, fraud or mistakes are easy to catch. If a child is supposed to be male, but a female’s sample is submitted, for example; in these cases, an accredited lab will suspend testing right away and start asking questions and/or request new samples. But the lab can’t always catch fraud, especially for at-home tests.  This is because a chain-of-custody process is not followed and DNA collection is in the hands of the customer rather than being supervised by an approved witness. This is also the reason why DDC does not put participant names on at-home reports and why reports for at-home tests are not court-admissible results: because there’s no way to verify whether the DNA the lab is given actually belongs to who the customer says it does.

Example: For at-home testing, the lab is answering this question: Is Possible Father A the biological father of Child A? If DNA for someone else is submitted as if it belonged to Possible Father A, then the answer may be very different that what it should have been, couldn’t it? The results from the lab are actually scientifically correct based on the samples provided, but if DNA for someone other than Possible Father A’s was submitted—which is fraud— the report could show an exclusion result for him even if he really is the father.

SOLUTION: When doing an at-home paternity test, we recommend that all participants witness each other swabbing their cheeks and the child’s cheeks and sealing the swabs in the paper envelope. It’s also important to go to the post office as a group to drop off the mailing envelope, thereby preventing any post-DNA-collection tampering. If participants live in different states and there is reason to believe someone might want to monkey around with results, it might be wise to consider choosing a legal, witnessed test instead.

Can a Saliva DNA Test Be Wrong for Paternity?

Most paternity tests, including DDC’s, use cheek (buccal) swabs rather than a saliva sample, and the two aren’t the same thing. A cheek swab collects cells from the inside of the cheek, and those cells hold the DNA the lab analyzes. That’s why DDC’s collection instructions ask each person to swab for a full 30 seconds per swab while avoiding the saliva-rich gum areas.

A swab that picks up a lot of saliva can end up too wet to seal right away. DDC recommends waving a wet swab in the air for 1 to 2 minutes before placing it in its paper sample envelope. With any self-collected sample, though, the bigger risk is the one covered above: making sure the right person’s DNA ends up on the right swab.

When Possible Fathers are Close Biological Relatives

When two alleged fathers are close biological relatives, they share a relatively large percentage of the same DNA.

• Father/Son: 50%
• Brothers: 25%
• Uncle/Nephew: 25%
• Grandfather/Grandson: 25%

Because of the shared DNA, when testing the minimum 16 DNA markers for paternity (DDC tests a minimum of 20), there is a slim possibility that the man who is not the possible father could match the child being tested at every location. This scenario can create what is called a “false positive” result. So can a paternity test be wrong? In this case: yes, even though lab processes were followed correctly. It demonstrates how essential it is to provide as much information as possible when setting up the test (see solution immediately below).

SOLUTION: Ideally, both possible fathers who share a close genetic link should test. But when only one man is available or willing to test, it is absolutely essential that the person ordering the test let the lab know before testing starts that there is another possible father who is a close relative of the man being tested and what the biological relationship is between the two men. This way, the lab can take this information into account as it does its analysis and generates a probability of paternity, plus it can test additional genetic markers if necessary in order to get conclusive and accurate results.

Identical twins are the one situation where standard paternity testing reaches its limit. Identical twins share virtually the same DNA, so a typical paternity test can’t tell which twin is the biological father. If the possible fathers are identical twins, tell the lab before testing begins.

Why It’s Important to Choose the Right Lab for Testing

Not every lab holds itself to the same standards. Accreditation means a lab’s practices and processes are held accountable by independent organizations that inspect it regularly and verify its testing methods and staff qualifications. Look for a lab that processes samples in-house and builds in its own accuracy checks, such as running each test more than once, which adds another layer of protection against error.

Frequently Asked Questions

If one DNA marker doesn’t match, does that mean he isn’t the father?

Not necessarily. Occasionally, a report shows a mismatch between the possible father and child at a single location but still shows a probability of paternity over 99%. That usually points to a natural mutation in either person’s genetic code at that location, and analysts account for mutations when they calculate the result. DDC’s guide to understanding paternity test results explains how to read each part of the report.

Does the mother have to be tested for a paternity test to be accurate?

No. A paternity test can be done with only the possible father and the child. DDC does recommend including the mother’s sample when possible. It shows the lab which half of the child’s DNA came from the mother, which makes the father’s contribution clearer and produces the strongest result.

Can a prenatal paternity test be wrong?

A prenatal test works differently from a cheek-swab test. A blood sample from the mother carries small fragments of the baby’s DNA, which the lab compares with a sample from the possible father. DDC’s prenatal paternity test examines more than 850 genetic markers and determines paternity with over 99.9% accuracy, starting as early as 7 weeks into pregnancy. It’s also the only AABB-accredited prenatal paternity test.

Paternity Answers You Can Rely On

DDC was the first lab to require every postnatal paternity test to be performed twice by independent teams, and the AABB honored DDC with its Commendable Practice Award for that process. Every result is reviewed by DDC’s in-house team of PhDs, and customers have trusted the company with more than 20 million DNA tests over the decades.

For child support, custody, Social Security or adding a name to a birth certificate, you’ll need a legal paternity test with witnessed sample collection. For personal peace of mind, a home paternity test uses the same lab process with cheek swabs you collect yourself, and results are ready in 1 to 2 business days once all samples arrive at the lab. A DNA specialist can help you decide which one fits your situation during a free consultation.

About DNA Diagnostics Center (DDC)

DNA Diagnostic Center is the world leader in paternity and relationship testing. We serve healthcare professionals, government agencies, and individuals around the world to determine family relationships with trusted accuracy.

More Questions? Don’t hesitate to call us: we’re here to help!