Circumstantial Evidence in a Drunk Driving Case

In the majority of DUI prosecutions, the state’s primary evidence is the result of a chemical sample obtained from the driver via a breath or blood test. But in about 20% of cases, the driver refuses to provide a sample. In these instances, the state relies on circumstantial evidence of intoxication both at the initial stop and during the arrest process. As is normally the case, this circumstantial evidence is vulnerable to a motion to suppress.

The Stop

It is difficult to win a motion to suppress the stop because the standard of proof of so low. The state need only prove that the officer had reasonable suspicion of criminal activity based on clearly articulable facts. That being said, there are significant holes in the facts that officers typically cite in these instances.

After the initial stop, the officer looks for indications of intoxication. These clues include:

  • Bloodshot Eyes: While this condition is evidence of intoxication, there are many other things, such as cigarette smoke and allergies, that cause bloodshot eyes.
  • Odor of Alcohol: The officer is often not specific as to whether the smell came from the driver’s breath or the inside of the vehicle. In the latter case, the odor simply establishes the fact that the driver was nearby someone who was drinking at some earlier point in time. Odor alone cannot establish that a person in under the influence of alcohol. This is due to the fact that alcohol itself has no odor. The smell coming from a person’s breath after consumption is due to congeners. Congeners are substances other than alcohol (which is strictly-speaking called ethanol in chemical nomenclature) produced during fermentation. These substances include small amounts of chemicals such as methanol and other alcohols (known as fusel alcohols), acetone, acetaldehyde, esters, tannins, and aldehydes (e.g. furfural). Congeners are responsible for most of the taste and aroma of distilled alcoholic beverages, and contribute to the taste of non-distilled drinks.
  • Slurred Speech: The officer does not know the defendant’s normal voice, so it is difficult to assess whether or not the speech is abnormal.

Even if a motion to suppress is unsuccessful, these arguments can help convince a jury that the officer may have been overanxious to arrest the defendant for DUI.

Field Tests

There are only three field tests approved by the National Highway Transportation Safety Administration for use in these cases.

The walk-and-turn (WAT) test assesses a suspect’s ability to follow directions and manual dexterity; loss of either function is evidence of intoxication. A common issue with the WAT is that the suspect is asked to walk an imaginary line. This task is much more difficult than walking along an actual line, like a parking lot stripe.

The one leg stand (OLS) suffers from similar weaknesses. It is difficult for anyone to balance on one leg in an uncontrolled environment when cars are zooming by and there are intense, flashing lights in the suspect’s eyes.

The horizontal gaze nystagmus (HGN) test is also unreliable when conducted in an uncontrolled environment. The flashing lights make it difficult for the suspect to follow a tip of a fingertip or pen, and also make it difficult for the officer to look for the “clues,” or involuntary eye movements that are allegedly evidence of intoxication.

Partner with Experienced Attorneys

Flaws in the state’s evidence make it difficult for a prosecutor to prove guilt beyond a reasonable doubt. For prompt assistance in this area, contact Glasgow & Olsson for a free consultation. After hours and jail visits are available.

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