Attacking Probable Cause Evidence in DUI Cases

Over the last 25 years, the Supreme Court has whittled away at the rule in Terry v. Ohio, which requires that officers base their investigatory stops (such as pulling over possibly intoxicated motorists) on “specific, articulable facts.” In 1990, the Justices ruled that officers could use properly set-up roadside checkpoints to pull over motorists simply because they were caught in a dragnet. Michigan Department of State Police v. Sitz basically held that the reasonable suspicion rule was not that important, and that decision set the table for subsequent cases like Utah v. Strieff (officers can detain people even if they have essentially no factual basis for doing so).

Reasonable suspicion was a low standard to begin with, and these decisions watered it down even further. However, the next pre-arrest phase is an entirely different ballgame.

Field Sobriety Tests

In about one in five cases, drivers refuse to provide breath or blood samples and officers are unable to perform a BAC test, so they must rely exclusively on the field sobriety tests (FSTs). Although there are many informal tests, like the finger-to-nose test, there are only three FSTs approved by the National Highway Traffic Safety Administration, and they all have various flaws.

  • Horizontal Gaze Nystagmus Test: Properly administered, the Horizontal Gaze Nystagmus test, which involves tracking an object with one’s eyes without moving one’s head, is about 80% accurate in predicting intoxication. Largely, these results are based on involuntary eye movements at certain angles. Conditions on the street or in a police station are hardly “controlled.”
  • Walk and Turn Test: Before administering the Walk-and-Turn test, or heel-to-toe walk test, officers are supposed to find flat, well-lit, and even surfaces that contain a parking lot stripe or other actual line, but they do not always offer these necessary accommodations.
  • One Leg Stand Test: Officers often assign failing grades on the One Leg Stand based on technicalities like starting before the directions are finished, holding up the wrong leg, or holding the leg at a slightly incorrect angle.

Chemical Tests

Actual numbers vary, but the conviction rate in test cases is usually about twice as high as in non-test cases. That is largely because of the per se DUI law, which means that drivers are guilty as a matter of law if their BAC exceeds a certain level. Since Breathalyzers have not changed very much since the 1950s in terms of the way they operate, they suffer from some of the same basic shortcomings as before.

  • Mouth Alcohol: Breathalyzers measure alcohol content in the breath and then estimate the blood alcohol level based on that reading. So, if the defendant burps in the 10 or 15 minutes before the test, the breath alcohol level goes through the roof and the results are often unreliable.
  • Acetones: Smokers and diabetics often have high acetone/ketone levels in their bodies, and many Breathalyzers register this substance as ethanol.
  • Calibration: As Breathalyzers get smaller and more complex, they require more maintenance and more operator skill.

Attorneys often partner with chemists to point out these flaws to a jury, and in many borderline BAC cases, some jurors will discount the test results.

Speak to Experienced Attorneys

Serious DUI cases require an aggressive defense. For a confidential consultation with an experienced criminal defense lawyer in Schaumburg, contact Glasgow & Olsson. After hours appointments are available.

(image courtesy of KOMUnews)

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