Posted on 10/17/16

For those suspected of DWI, law enforcement employs various on the spot methods, or field sobriety tests, to determine a person’s sobriety. If arrested on the suspicion of DWI and are compelled to take these tests, know that these tests may be inaccurate and cannot prove guilt.

Standardized Tests

Texas law enforcement employs three standardized field sobriety tests:

  • Horizontal gaze nystagmus (HGN), which means bouncing eye movement. It is an involuntary rapid oscillation of the eyeballs in a horizontal, vertical, or rotary direction. It suggests alcohol use, though may be due to psychological or physiological reasons.

  • One leg stand.

  • Walk and turn.

How to Administer Field Sobriety Tests

A police officer must administer the test in a well-lit area or by illuminating the suspect’s face with a flashlight. The suspect should not be faced toward blinking lights or passing cars. HGN cannot be used to quantify the blood/alcohol content (BAC).

Other tests, which are non-standard but routinely used by police officers include:

  • Reciting the alphabet;

  • Fingerprinting;

  • Photographing;

  • Handwriting;

  • Voice exemplars

Note that these tests are not 100% accurate and are not compelling evidence by trial. In fact, a Texas Appellate Courtreversed a DWI conviction when it questioned the reliability of the VGN’s scientific reliability, admission of officer’s testimony regarding the VGN test, and regarding defendant’s impairment.

Implied Consent to Breath and Blood Tests

The Texas Transportation Code has an implied consent law that requires drivers suspected of DWI to submit a sample of their blood or breath for testing. If a person is willing to risk license suspension then that person can refuse to submit a sample.

Texas case law considers involuntary breath and blood tests. In a2011 case, the Texas Criminal Court of Appeals addressed involuntary consent for a blood draw. After an accident, a police officer smelled alcohol on the defendant’s breath and did not ask the defendant to perform any field sobriety tests, but believed that the defendant was subject to a mandatory blood draw. The officer told the defendant that the defendant can voluntarily go to the nearest medical facility or be taken into custody and his blood would be drawn. The defendant then consented. The trial court found that the defendant caused the accident, and that he believed he was under arrest when he gave consent. The Court ruled the blood draw involuntary and therefore not admissible evidence.

Attacking Breath and Blood Tests

At trial for DWI, a defendant can question the results of a field sobriety test in the following ways:

  • Scientific accuracy of the test given;

  • Margin of error for such tests;

  • Machine or testing apparatus malfunction;

  • Other factors that can affect the test’s reliability; examples are mouthwash, fever, burping, individual differences, poppy seeds, purging of previous contaminates, radio transmitters near the machine.

If you are arrested for DWI, know that you have rights. You are innocent until proven guilty. Do not do this alone. Contact the criminal defense firm of Christopher Abel, an experienced Dallas-area criminal attorney.

(image courtesy of Oregon Department of Transportation)

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