Maryland DUI

DUI Tests and False Positives

One of the most incriminating pieces of evidence that can be used against a defendant to secure a DUI conviction is that of a “positive” blood or breath test; that is, results of a DUI test that reveals that the defendant was indeed operating their vehicle with a blood alcohol concentration (BAC) of .08 percent or above. What many defendants don’t realize, however, is that these tests can deliver false positives, resulting in strong evidence against a defendant that is neither accurate nor fair. At The Law Office of Jonathan R. Fellner, L.L.C., our skilled DUI defense lawyer is prepared to help you fight back against a false positive and defend yourself against DUI charges.

Factors that Can Lead to Breathalyzer False Positives

The results of breathalyzer tests are often used by arresting officers in order to establish probable cause to arrest a defendant on a DUI charge. They are also often used later by the prosecution to secure a DUI conviction. A Preliminary Breath Test (PBT) can be administered roadside but can never be used by the prosecution against you in Maryland; conversely, if the result is in your favor, you can use it as evidence.

An officer may not perform or interpret the results of a breathalyzer test correctly or may not understand circumstances (like certain medications) that can affect results.

In addition to administration errors, other factors that can lead to breathalyzer false positives might include:

  • Improper calibration of breathalyzer device. Proper calibration of a breathalyzer device is critical to obtaining an accurate reading. What’s more, devices must be calibrated on a regular basis to ensure that they maintain accuracy. If there is evidence that the device was faulty or wasn’t calibrated within a reasonable amount of time prior to being used to obtain a BAC reading on a defendant, the evidence may be inadmissible.
  • Improper timing of testing. If a person has had alcohol and any alcohol remains within their mouth, this can affect the results of a breathalyzer reading. As such, police officers are required to wait 20 minutes from the time that the individual is stopped before administering the breathalyzer test. What’s more, if the individual vomits or burps during the 20-minute time period, the clock must be restarted.
  • Sometimes, a breath (or blood) sample can be contaminated by other substances that affect the results, such as certain chemicals. If contamination of a sample occurs, the test should be re-administered, as the original will not be accurate.
  • Health conditions and medications. Certain health conditions and medications can contribute to the risk of false breathalyzer positives. If you have certain health conditions or use certain medications, you should talk to your lawyer about the potential of these affecting your breathalyzer test.

 Standardized Field Sobriety Tests (SFSTS)

The result of a breathalyzer test is not the only type of evidence that can be used against a suspect; the results of field sobriety tests are often used against individuals as well. However, the room for error when administering these tests is even greater than with breathalyzer tests; there is research that shows high field sobriety test fail rates amongst non-intoxicated individuals.

The three SFSTS most often used by police officers are the Horizontal Gaze Nystagamus (HGN) the Walk and Turn and the One Leg Stand.

HGN- Police are trained to use a penlight to follow your eyes to determine if there is involuntary jerking of the eye. Maryland Courts have ruled that this test requires expert testimony but as a practical matter, the Courts have ruled that the test can only be accepted-if performed properly-to show that the presence of alcohol.

One Leg Stand- The officer requests that you stand with one foot about 6 inches off the ground with your toe pointed. While maintaining your balance you have to count by thousands for 30 seconds, although the police just tell you to count until they say to stop. You must keep your arms at your side and look down at your foot. Officers are trained to look for the following: 1) putting your foot down before the test is finished; 2) swaying while trying to maintain balance; 3) using your arms for balance and; 4) hopping while trying to stay balanced.

Walk and Turn- In the walk-and-turn test, you are instructed to take nine steps in a heel-to-toe fashion in a straight line.  After the ninth step, you then must turn on one foot and return in the opposite direction in a heel-to-toe fashion.  While you are completing the walk-and-turn test, the police officer is making note of the presence of the following seven indicators of impairment: 1) whether you are unable to maintain your balance while listening to the officer’s instructions; 2) whether you begin walking before the officer has completed the instructions; 3) whether you stop while walking in order to regain your balance; 4) whether you actually touch your feet heel-to-toe; 5) whether you use your arms to maintain your balance; 6) whether you lose your balance while turning and; 7) whether you take an incorrect number of steps.

Let Our Aggressive Maryland DUI Lawyer Help You

Being charged with a DUI in Maryland is scary in and of itself and can lead to serious questions about what the outcome of your case may be and what your future will look like. If the evidence that is being used against you is faulty, you may be frustrated and angry. Before you do anything else, call our skilled and experienced DUI lawyer at The Law Office of Jonathan R. Fellner, L.L.C. to learn more about your options for fighting back against a false DUI test positive.

Attorney Jonathan Fellner has been practicing criminal defense law for over two decades and has a strong track record of success in this area of the law. To schedule a consultation with attorney Fellner today, please call our office directly at ((301) 602-0835, email us at, visit our office in person, or send a secure and confidential message through our online contact form.

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