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posted on 9/10/17

Although most drivers provide either a breath or blood chemical sample, about 20% of DUI cases rely exclusively on circumstantial evidence. Sometimes, information gathered at the one-on-one or checkpoint stop, which we examined in a previous post, bleeds over into the next phase of the prosecution, which is probable cause for the arrest. Most probable cause evidence comes from the three scientifically-recognized field sobriety tests.

Prior to the Stop

Erratic driving is nearly always an issue, unless the officer pulled over the driver because of a third-party tip from another officer or a civilian, and even in these cases, erratic driving may be a factor. This category includes a wide variety of behaviors, from speeding to making an illegal turn or lane change.

Undoubtedly, erratic driving may be an indication of alcohol impairment because people who drink have problems concentrating and controlling their motor skills. Erratic driving may also indicate that the driver is sleepy, lost, unfamiliar with the surroundings, nervous because a police officer is nearby, or a host of other things that are not illegal.

Most all police reports also note an odor of alcohol, bloodshot eyes, and a lack of physical coordination (perhaps slurred speech). Once again, there may be explanations for these behaviors independent of alcohol.

  • If the alcohol odor emanates from the defendant’s car or clothes, the scent only establishes that the driver had been around people who had been drinking.
  • Fatigue, cigarette smoke, allergies, and bright lights (like the one the officer is probably shining in the defendant’s face) can all cause bloodshot eyes.
  • Some people are naturally uncoordinated and/or clumsy, especially when they are anxious and/or upset.

These items are usually sufficient to establish reasonable suspicion for the arrest, but probable cause is a much higher standard, so things that are easily explained away, such as questionable driving habits, may be insufficient at this point.

The Field Sobriety Tests

To fatigue the driver and also to create negative momentum, officers usually administer a full battery of tests in excess of the ones that the National Highway Traffic Safety Administration has approved as both scientifically sound and logically reliable. Many times, these tests, such as reciting the ABCs, are either inadmissible or admissible only for limited purposes at trial.

While they are universally recognized as reliable, the three approved FSTs are also subject to challenge.

  • Walk and Turn: Like many other FSTs, the WAT (which is sometimes called the heel-to-toe walk) measures both physical and cognitive abilities. Some physical “clues” include using arms for balance, swaying, and falling over; some cognitive clues include starting with the wrong foot and taking the incorrect number of steps. Subjects who exhibit two or more clues were intoxicated in 79% of the cases examined in a 1998 study.
  • One Leg Stand: Perhaps even more so than some other tests, officers often measure “passing” and “failing” the OLS on strict technicalities, like holding the leg up at slightly the wrong angle or dropping it a few nanoseconds early.
  • Horizontal Gaze Nystagmus: The aforementioned 1998 test also concluded that 88% of people who are unable to follow moving objects with their eyes without moving their heads are intoxicated. However, according to the AAA, “HGN may also indicate consumption of seizure medications, phencyclidine, a variety of inhalants, barbiturates, and other depressants.”

Furthermore, the accuracy of these tests depends on both the skill of the person who administers them and the conditions in which they take place. Questions in either area affect the reliability of the results.

Count on Aggressive Lawyers

Circumstantial evidence is always subject to different interpretations, and in DUI cases, the jury’s interpretation is the only one that counts. For a confidential consultation with an experienced criminal law attorney in Schaumburg, contact Glasgow & Olsson.

(image courtesy of Zach Meaney)