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What Can Cause a False Positive on a DUI Drug Test?

Posted on in DUI/DWI

Knox County DUI defense attorneyA majority of DUI stops are related to alcohol. Alcohol is both legal for adults over 21 years old and relatively ubiquitous, especially around the holidays. It is also relatively easy to detect during a DUI stop. Alcoholic beverages typically produce a strong odor, often accompanied by obvious signs like slurred speech and an unsteady gait. Drugs can be more difficult to detect following a DUI stop. 

Police officers typically rely on chemical or lab testing to determine whether a person is under the influence of another narcotic substance. However, drug tests are not perfect and are not always a clear indication of whether a person is currently intoxicated. If you have been charged with a drug-related DUI, an attorney can help you build a strong defense. 

What Can Cause False Positive Results on a DUI Chemical Screening?

It is not uncommon for a person who is not actively under the influence of any substance to still test positive. Even certain over-the-counter medicines can cause false-positive results for various substances. Here are a few things that could lead to a false positive drug test result:

  • Medication - Many medications, both prescription and over-the-counter, can cause a false-positive result on a drug test. Cold and cough medicines that contain dextromethorphan, for example, can sometimes trigger a positive result for opiates or PCP. Some common non-narcotic prescription medications, such as gabapentin, can also cause you to test positive for opiates due to their similar workings.
  • Foods - It is not a myth that poppy seeds can cause a person to test positive for opiates. Consuming bagels, cookies, or other foods that contain larger amounts of the ingredient can in fact make you fail a drug test. 
  • CBD - CBD oil, derived from a non-psychoactive substance found in cannabis, is legal for use in Tennessee. It may contain up to 0.3% THC, which is a psychoactive substance. However, this is a small enough amount that it should not cause impairment. Yet, it could still cause you to test positive and lead police to believe that you are under the influence of cannabis. 
  • Testing error - Testing errors are a common cause of false positives. A mistake in any part of the testing procedure can cause contamination or interference that leads to a false positive. These types of mistakes are rarely noticeable at the time, but may be discovered upon closer investigation. 

If you were told that you tested positive for a narcotic and have been charged with DUI, it is important that you take the situation very seriously. Tennessee is notoriously harsh in dealing with even first-time DUIs. 

Call a Knox County DUI Defense Attorney

The Law Office of William F. Evans is skilled at building strong defenses for those accused of drug-related DUI. Our experienced Knoxville DUI lawyers understand how complicated chemical drug testing can be and are skilled at challenging potentially inaccurate results. Call our law office at 423-449-7980 so we can schedule your free consultation. 



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