Challenging Circumstantial Evidence of Intoxication

Lawyers and witnesses can greatly influence the outcome of a criminal trial by the words they use, and this dynamic is particularly present in DUI cases that involve Field Sobriety Tests.

In these trials, the officer always says that the suspect “failed” the tests, and that word gives jurors the impression that the suspect performed extremely poorly. That is because most of us believe that people fail tests when they get most of the questions wrong. But when officers use this word, they really mean that the suspects did not perfectly perform the tests, and it is important that the jury understand the difference between imperfection and failure because these are two very different concepts.

Unapproved FSTs

In addition to the terminology, many officers use a battery of tests, assuming that more tests mean more opportunities to fail. Therefore, officers sometimes force suspects to perform non-standardized FSTs, including:

  • Reciting a portion of the ABCs,
  • Counting backwards from one number to another one, and
  • Finger-to-nose balancing test.

Often, officers place the unapproved tests before the approved ones, in the hopes that the suspects will become fatigued both mentally and physically, and thus perform poorly on the tests that really matter.

In Illinois, non-standardized FSTs are generally admissible, although the judge may limit them to the issue of whether or not the stop was valid. Even if they are admissible for purposes of proving intoxication, their status as unrecognized means that the results and applications are suspect, at best.

Approved FSTs

The National Highway Transportation Safety Administration recognizes three Field Sobriety Tests, and these three FSTs usually have the greatest impact on the jury’s finding of intoxication because there is more scientific evidence in support of these tests.

The agility tests, the One Leg Stand and Walk and Turn, are both divided-attention tests that measure physical and cognitive abilities. In the OLS, the suspect must balance on one leg for a fixed number of seconds; for the WAT, the suspect must walk a line heel-to-toe for a certain number of steps. Officers often testify that the suspect “failed” the test based on technicalities like:

  • Starting before the instructions are fully complete,
  • Beginning with the right leg instead of the left, or vice versa,
  • Taking too many steps,
  • Holding the leg at the wrong angle, or
  • Suspending the leg for more than the allotted time.

These shortcomings are certainly evidence of impairment, but not conclusive as to a complete loss of mental or physical faculties.

The third test is the Horizontal Gaze Nystagmus. Suspects follow a point, such as a fingertip, by moving their eyes without moving their heads. In laboratory tests, the HGN is about 90% effective in predicting intoxication; however, most HGNs are conducted in the field, where conditions are completely uncontrolled. Some of these conditions include:

  • Flashing patrol car lights,
  • Bright headlights and “take-down” lights, and
  • Adverse environmental conditions, like darkness.

These deficiencies, plus the fact that so many substances other than alcohol create a false positive, make the test results less credible in the eyes of a juror that already has some doubt.

Partner with Zealous Attorneys

It is difficult for prosecutors to win DUI cases premised entirely on circumstantial evidence. For a confidential consultation with an experienced Schaumburg criminal defense attorney, contact Glasgow & Olsson. We routinely handle cases in Cook County and nearby jurisdictions.

(photo courtesy of Gabriel Volonte)

This entry was posted in: 

And tagged: