However, even under optimal conditions and clear instructions from the officer, the FSTs are not conclusive proof of impairment. Although the FSTs can serve as one piece of a much more complex DUI puzzle, the burden on the state to prove each of the elements of DUI beyond a reasonable doubt require far more then an officer’s observations of the FSTs.

Can Prior Injuries or Diagnosis Explain FST Failure?

In some cases, the lack of balance, which plays a significant role in all 3 of the FSTs, can be explained due to medical conditions that impact a defendant’s ability to maintain a balanced position, especially under the stressful circumstance of a DUI investigation.

Have you suffered a lower body injury? Have you suffered a concussion or other brain injury. Do you have high sensitivity to light or occasions of Vertigo? If so, it is important to gather records of these injuries through your medical providers in order to provide some context as to the failure of the FSTs.

Did a Car Accident Occur Prior to FSTs?

In some cases, a defendant is requested to perform FSTs shortly after they were involved in a motor vehicle accident. Although there is no hard and fast rules prohibiting FSTs from being taken after an accident has occurred, the injuries sustained as a result of the crash can cast into doubt the validity of the tests.

Even in situations where the defendant is not transported to the hospital, it is still important to be evaluated by a medical professional in order to determine the extent of the bodily damage that was sustained. If a defendant declines all treatment, this important evidence as to their condition at the time of performing FSTs is lost, making it harder to explain to a judge or jury the impact this accident had on balance and the comprehension of officer instructions.

Age and Weight Can Raise Doubt as to FST Performance

Although not considered definitive, the National Highway Safety Association has found that individuals over the age of 65 and those who are 50 or more pounds overweight may have a more difficult time performing the FSTs even if not under the influence. Officers are encourage to take these factors into consideration when determining probable cause for a DUI arrest.

Even if the defendant is still arrested, using the NHTSA recommendations can cast doubt as to the validity of the FSTs, especially in cases where additional medical conditions are also a concern.

Gather Your Medical Records Early in a DUI Prosecution to Determine Whether a Defense Exists to the FSTs

It is not illegal to be off balance. Explaining the underlying cause of imbalance through medical testimony can be an impactful way to argue to a jury that the results of the FSTs in a Vermont DUI prosecution should be significantly discounted, or, in some cases, all together ignored. By putting together a medical chronology that supports a medical defense to a DUI, a defendant may be able to show that alcohol or drugs were not the underlying factor of their roadside behavior.

The information contained in this post is for informational purposes only. Any reader who has specific questions about the DUI or any other legal process should consult with their own private attorney.

There have been court cases in which this process has been used as a defense when the defendant was a type 1 diabetic and had high levels of ketones in their blood, which therefore were producing this effect where acetone or potentially Isopropanol was detected in the breathalyzer test causing a false positive.   “If ketoacidosis develops, the diabetic person may experience a myriad of symptoms including dry-mouth or fruity breath odor, and keytones on the breath could theoretically register as ethyl alcohol on BAC breath tests. Brick, Diabetes, Breath Acetone and Breathalyzer Accuracy: A Case Study, 9(1) Alcohol, Drugs and Driving (1993). In Michaels v. State ex rel. Dep’t of Transp., the defendant, a type 1 diabetic, claimed his blood-alcohol levels may have been affected by ketoacidosis. 2012 WY 33, ¶ 8, 271 P.3d 1003, 1006 (Wyo.2012).” Supreme Court of Wyoming.

Robert Olaf ANDERSON, Appellant (Defendant), v. The STATE of Wyoming, Appellee (Plaintiff) 2014.

There are other circumstances where this chemical process will happen in the body of people without a diagnosis of type 1 diabetes.  Diets that are very low carb or no carb “ketogenic” diets, which are rapidly becoming a norm for use in weight loss can trigger this same chemical reaction in the body, producing a buildup of ketones (or ketoacidosis) leaving byproducts that look like alcohol to a breathalyzer machine. “The National Highway Traffic Safety Administration (NHTSA) in the USA has found that dieters and diabetics may have acetone levels which are hundreds and even thousand of times higher than those in others (5). Acetone is one of the many substances that can be falsely identified and measured as ethanol by some breathalyzer machines.”  Tazhmoye V., Crawford Donovan, A. McGrowder, Joan M. Rawlins: An assessment of falsely convicted type 1 diabetics in Jamaica by using the breathalyzer test, 2011.

Low calorie diets that may still utilize carbs for fuel can also cause this process, (Very Low Calorie Diet) “VLCD treatment leads to ketonemia with high concentrations of acetone, acetoacetate and beta-hydroxybutyrate in the blood. The interlock device determines alcohol (ethanol) in breath by electrochemical oxidation, but acetone does not undergo oxidation with this detector. However, under certain circumstances acetone is reduced in the body to isopropanol by hepatic alcohol dehydrogenase (ADH)”.  Int J Obes (Lond). 2007 Mar;31(3):559-61. Epub 2006 Aug 8.False-positive breath-alcohol test after a ketogenic diet.Jones AW1, Rössner S.  

Based on the factors above which highlight the possibility for the human body to naturally produce certain chemicals that would be mistaken for ethanol in a breathalyzer test, one might conclude that with a growing population struggling with an obesity epidemic, an increasing amount of people adopting a low carb or no  carb, “ketogenic” diet, and he possibility of an extreme low calorie diet as a result of poverty, that the incidents of false positive breathalyzer tests in defendants who have consumed under the legal limit of alcohol, (or no alcohol at all) but may present with this metabolic picture, could be greater than law enforcement take into account. That being said, there is no reason to trust a breathalyzer as the only evidence that a driver was intoxicated.  A defense attorney, who practices in DUI should take into account the variety of physiological factors that have been scientifically tested more recently, which may indicate an error in the current system for testing a driver’s BAC on the roadside.