Are False Positives Possible on a DUI Test?

DUI Tests & False Positives

dui and false positivesIf you are pulled over for DUI in Virginia, the police may ask you to take several types of DUI tests to help them determine whether you are legally drunk. Many people don’t realize that they aren’t legally obligated to take a roadside test (a post-arrest test is different).

If you do consent to these tests and they aren’t to the officer’s liking, you will probably be arrested for DUI. Unfortunately, there are a host of reasons why people fail these various tests because of false positive results. The good news is that an experienced and aggressive Virginia DUI attorney can protect your rights and challenge these results.

Common Reasons for Failing Field Sobriety Tests

Field sobriety tests are a set of so-called standardized roadside tests that are meant to evaluate sobriety. These tests involve having already terrified drivers going through a series of exercises on an unfamiliar roadside while being observed by intimidating law enforcement officers.

The tests, which usually ask drivers to perform physical feats and contortions, are fallible at best. They can produce false positive results for any number of reasons. These include the uneven surface of the road, adverse weather and traffic conditions, and any interfering medical or physical limitations of the test subject.

False Positive Results on DUI Breath Tests

Many people, including law enforcement, put entirely too much faith in technology. For the most part, the DUI threshold in Virginia is a BAC of 0.08% or higher and the police will use a DUI breath test to confirm their suspicions about your status. Unfortunately, these tests can also produce false positive results thanks to several factors:

  • Poorly-Calibrated Equipment. Police are required to keep DUI testing equipment carefully calibrated to ensure the most accurate results. If you can prove that their equipment was outside the parameters for servicing and calibration, you may be able to challenge a test.
  • Test Administered Too Soon. When you drink alcohol, some of it remains in your mouth. Police are not supposed to test for DUI until at least 15 minutes after you have been observed either drinking, burping, or vomiting. If they test too quickly, the results may be skewed.
  • Your BAC Was Rising. Alcohol can take up to three hours to fully absorb in your system. This means that you could have been below the legal limit when driving, but above it later when tested for DUI with a machine.
  • Your Diet Impacted the Result. Your chosen diet can have an effect on a DUI test, having the machine mistake your breath’s acetone level for alcohol. Low and no-carb diets and people who are fasting are at a higher risk of triggering these types of false positive results.
  • A Medical Condition Affected the Result. Many medical conditions can impact a DUI test result. These include but aren’t limited to acid reflux disease and uncontrolled diabetes.
  • Test Was Improperly Administered. DUI machines are complex pieces of equipment that are only supposed to be operated by trained professionals. A false positive could appear if a test is administered by someone who isn’t trained or was negligent in the test handling.

Challenging DUI Test Results

Because DUI tests can be subjective, having the right criminal defense attorney in your corner is critical. Depending on your situation, it may be possible to challenge these test results if they are inaccurate. You may need to show proof that there was a flaw in the equipment, the terrain or weather impacted a test, or that you have a medical or other condition that interfered with the test results.

A DUI lawyer can ask specific questions of the officer that administered the test as well as anyone on the police force that is charged with handling DUI machine maintenance or calibration. Another common challenge is that test subjects are not given the full information about their rights before being given these tests.

Speak with an Experienced Virginia DUI Attorney

A DUI conviction can have lasting consequences, and this is not something that you want to leave to chance, particularly if you have positive DUI tests to back up the arrest. Whether or not you believe that those tests were faulty, you need a skilled Virginia DUI attorney who will advocate for your rights.

The Pack Law Group understands Virginia’s complex DUI laws and will use aggressive and proven means in your defense. If your arrest took place in Central Virginia’s Roanoke, Lynchburg, or Bedford counties, contact Pack Law now at 540-586-7225 to schedule a consultation.


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