6 Common DNA Testing Errors You Should Know About

DNA testing is often viewed as the gold standard in forensic science, trusted by courts, medical professionals, and families alike. Its results carry immense weight—shaping child custody decisions, determining guilt or innocence, and even reuniting long-lost relatives. But as reliable as these tests may seem, they aren’t flawless

Many people assume that once a DNA test result is in, the matter is settled. The truth is, errors can and do happen. From improper handling to lab mistakes, there are many ways a seemingly airtight result can turn out to be wrong. And the consequences? They can be life-altering.

This is exactly why so many people find themselves asking, “Can DNA tests be wrong?” The short answer is yes. The long answer is more complicated—but it starts with understanding how and why these errors occur in the first place.

In this article, we’ll break down six common types of DNA testing errors and what you can do if you suspect a test result may be inaccurate. Being informed could help you prevent a mistake—or correct one that’s already happened.

1. Sample Contamination

One of the most common and preventable errors in DNA testing is sample contamination. DNA samples can easily be tainted by outside genetic material—whether from the environment, lab personnel, or even from improper storage conditions. When this happens, the test results can reflect more than one individual’s DNA, leading to confusing or completely inaccurate findings.

In criminal cases or paternity disputes, this type of error can cause irreversible harm. Unfortunately, unless someone audits the testing process, contamination may go unnoticed until it’s too late.

2. Human Error in the Lab

No matter how advanced the technology, people are still involved—and people make mistakes. Lab technicians may label samples incorrectly, mix them up, or even input the wrong data during analysis. In some high-volume testing labs, technicians are working under tight deadlines with hundreds of samples at a time, increasing the risk of slip-ups.

This is why oversight and third-party verification are so important. One wrong keystroke or mislabeled vial can completely change the outcome of a test.

3. Faulty Equipment or Inadequate Calibration

Like any technical process, DNA testing depends on precise instruments. If the equipment isn’t calibrated regularly or malfunctions during analysis, the results can be compromised. Sometimes the software used to interpret the data has bugs or compatibility issues that skew readings.

In legal scenarios, opposing counsel may challenge DNA results based on questions about equipment quality or lab certifications. Always check whether the lab follows industry-standard protocols and holds proper accreditations.

4. Low-Quality or Degraded DNA Samples

Not all DNA samples are created equal. A swab from inside the cheek will usually provide clean, high-quality DNA. But samples collected from old clothing, bones, or crime scenes may be partially degraded or contain only trace amounts of DNA. This can lead to partial matches or inconclusive results.

In some cases, the DNA sample may be so limited that labs use what’s called “low copy number” testing, which is highly sensitive but also more prone to error. Results from degraded samples should always be interpreted cautiously.

5. Misinterpretation of Results

Even when the science is solid, interpretation is still subjective to a degree. For instance, close relatives share a significant portion of their DNA, which can lead to false positives if the analyst isn’t careful. Additionally, test results sometimes include probabilities and statistical language that can be misunderstood by the courts or the people involved.

An experienced legal team or independent expert can help ensure results are being read correctly, especially in high-stakes cases involving custody or criminal charges.

6. Laboratory Bias or Conflict of Interest

While it’s uncomfortable to consider, not all labs operate with complete objectivity. Some are affiliated with one side of a legal case—such as a state prosecutor’s office or a private testing service hired by one parent in a paternity case. When this happens, there’s a risk of unconscious bias affecting how results are interpreted or presented.

For peace of mind, request testing from a neutral, accredited lab—or better yet, get a second opinion from an independent expert.

Final Thoughts

DNA testing has revolutionized the legal and scientific landscape, offering powerful evidence in many contexts. But it’s far from perfect. From contaminated samples to human error and biased interpretations, there are multiple ways errors can slip through the cracks.

The key takeaway? Questioning a DNA result doesn’t mean rejecting science—it means demanding precision, fairness, and accountability in how that science is applied.

If you’ve ever wondered if DNA tests can be wrong, the answer is clear: yes, they can. And if you believe your result may be flawed, don’t stay silent. Reach out to legal professionals and genetic experts who can help you explore your options, challenge the findings, and—if needed—set the record straight.