DUI Defense – “Objective” Signs of Alcohol Intoxication

Last Modified: June 18, 2024

DUI Defense – “Objective” Signs of Alcohol Intoxication

Odor of alcohol

The odor of alcohol on a driver’s breath is one of the first clues an officer relies upon to both:

  • Initially determine that a driver has been drinking.
  • Provide justification for the start of a DUI/DWI investigation.

However, this may not be an accurate test. In a study on the ability to detect alcohol use by odors, 20 experienced officers were asked to detect an alcohol odor from 14 subjects with a Blood Alcohol Concentrations (BAC) ranging from 0-0.13%. Subjects were hidden behind a screen and asked to blow through a 6-inch tube, with the police officer’s nose at the end of the tube. Officers were unable to identify the beverage type (e.g. beer, wine, bourbon or vodka) and odor strength estimates were unrelated to BAC levels.

Slurred speech

Slurred speech is traditionally considered an indication of impairment. However, research indicates that the characterization of an individual’s speech as slurred may be more subjective than anticipated.

In a study of the ability of speech to determine degree of alcohol intoxication subjects (light, moderate and heavy drinkers) were asked to speak at three different times: during a learning phase, when sober, and at four Blood Alcohol Concentrations (BAC) levels. Subjects exhibited significant changes in speech as the alcohol level increased. However, the authors warn that these speech patterns “cannot be viewed as universal since a few subjects (about 20%) exhibited no (or negative) changes.”

The effect of simulated sober or intoxicated speech was also evaluated, to determine if listeners could determine which utterances were made in the intoxicated condition. Actors were asked to produce several types of controlled utterances at various simulated alcohol levels, during actual alcohol intoxication, and attempting to sound sober when at the highest actual BAC level. Listeners rated the actors as being more intoxicated when the actors were sober but simulating drunkenness (88% more often than when they actually were intoxicated). In a second study, the actors were judged as sounding less inebriated than reality 61% of the time.

For another study the testers made audio recordings of male talkers uttering sentences under a sober condition and an intoxicated condition. Two types of experiments were made: (1) listeners were asked to listen to a matched pair of sentences, and to identify which sentence was uttered while the speaker was intoxicated, and (2) Indiana State Troopers and college undergraduates were asked to judge whether individual sentences were produced by a sober or an intoxicated speaker. The authors found that there were definite changes in speech articulation between sober and intoxicated conditions.

However, not all researches agree that slurred speech or changes in speech characteristics are evidence of intoxication, especially at low levels. Eleven subjects were asked to read a text in both sober and alcohol intoxicated conditions. By means of statistical analysis, various speech parameters were evaluated. The authors concluded that, on the basis of the results, “application of acoustic analysis in forensic medicine for recognition of low-level alcohol intoxication is considered inexpedient.”

Another researcher analyzed recordings made by Captain Hazelwood, the captain of the Exxon Valdez, recorded at several points around the time of the accident at Prince William Sound, Alaska. Acoustic-phonetic analysis of the captain’s speech recorded before, during and after the accident revealed a number of changes in speech. However, the authors warn of the limitations in making inferences concerning the state of the speaker upon the basis of phonetic data.

Red/watery eyes

Red or watery or glassy eyes can occur either during intoxication or sobriety.

These symptoms may manifest with other conditions such as wind irritation, fatigue, eye irritation, or emotional state.

In addition, there is no correlation of red or watery or glassy eyes with Blood Alcohol Concentration (BAC) because the effects may be present in subjects who are not intoxicated.



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