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Undermining the FSTs in Parker County

Whether or not the defendant provides a chemical sample, the Field Sobriety Tests are important in DWI cases.

As for test cases, the FSTs allow Parker County prosecutors to establish probable cause. A mere suspicion of DWI, such as erratic driving or an odor of alcohol, is usually not enough to support an arrest. Officers must have clear evidence that the defendant was too impaired, from a physical or mental standpoint, to safely operate a vehicle.

In about 20 percent of DWI cases, the defendant refuses to provide a sample. In these cases, the FSTs usually serve as evidence of intoxication. The state must prove intoxication, and every other element of every other criminal offense, beyond a reasonable doubt.

So, the more a Weatherford criminal defense attorney can undermine the FSTs, the easier it is to successfully resolve these cases. This resolution could be a dismissal of charges, plea to a lesser-included offense, or a not-guilty verdict at trial.

Horizontal Gaze Nystagmus

The DWI eye test measures involuntary pupil movements at certain viewing angles. If a subject exhibits more than two clues, the subject probably has nystagmus. Alcohol and/or drug intoxication causes nystagmus.

This condition is also called lazy eye. Many people have nystagmus, but they do not know it because the symptoms are so mild. Additionally, substance intoxication is not the only cause of impairment. In fact, it is not even the leading cause.

Because of these weaknesses, many Parker County judges only admit HGN test results for limited purposes.

Walk and Turn (WAT)

This test is probably the most difficult one. Subjects must stand heel to toe, walk a straight line heel to toe, turn around, walk back, and then hold the pose until the officer ends the test. Intoxication clues include:

  • Beginning the test before the officer says "start,"

  • Using arms for balance,

  • Swaying,

  • Stumbling,

  • Talking the incorrect number of steps,

  • Falling off the line,

  • Failing to walk heel-to-toe, and

  • Ending the test before the officer says "stop."

Conditions greatly affect this test. It's very difficult to walk an imaginary line heel-to-toe, especially if the surface is not perfectly flat and the lighting conditions are anything less than ideal.

One-Leg Stand (OLS)

Much like the WAT, the OLS is a divided attention test which measures both physical dexterity and mental acuity. Many scientists claim that intoxicated people cannot multitask in this way.

Also much like the WAT, the OLS is almost impossible to perform if the defendant has any physical limitations. Additionally, officers often administer this test last, when the defendant is mentally and physically fatigued.

To successfully complete this test, subjects must elevate one leg at about a 45 degree angle for about fifteen seconds. Intoxication clues include swaying, using arms for balance, holding the wrong leg up, and putting the leg down too early.

Evidence in DWI cases is not always compelling. For a free consultation with an experienced criminal defense attorney in Weatherford, contact Herreth Law. Home and jail visits are available.

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