Most drivers provide chemical samples, usually breath samples, upon request. The conviction rate in these cases is over 80 percent. The rate is close to 100 percent in blood test cases. But in non-test cases, the Tarrant County conviction rate plummets to 45 percent.
The reason is simple. Without a chemical test result, prosecutors cannot use the per se section of the DWI law. Instead, they must prove that the defendant lost the normal use of mental or physical faculties.
Such a showing is difficult to make, especially considering the high burden of proof in these situations (beyond a reasonable doubt).
To meet this burden, prosecutors normally rely on the field sobriety tests. Different law enforcement officers apply different tests, such as the finger-to-nose test and the reciting-the-ABCs test. But the National Highway Traffic Safety Administration has only approved three FSTs, and the prosecutor's case usually comes down to these three tests.
Walk and Turn
In the heel-to-toe walk test, the defendant must walk a certain number of steps in a straight line heel to toe. During the test, officers look for clues of intoxication, such as failing to walk heel-to-toe, stumbling, or swaying. There are some other clues as well, such as starting with the wrong foot or beginning the test before the officer says "start." Many jurors consider these things to be technicalities.
Test conditions are the biggest problem with the WAT. It is much harder to walk an imaginary line heel-to-toe than it is to walk an actual line. Furthermore, roadside WAT tests take place in the dark as cars whiz past at high speeds. These conditions are hardly controlled.
One Leg Stand
Much like the WAT, the OLS is a divided attention test that measures both physical dexterity and mental comprehension. Generally, intoxicated people cannot multitask, so these kinds of tests are quite difficult. Defendants must lift one leg off the ground for a certain amount of time without losing their balance or moving their elevated legs.
Test technicalities, like holding the leg at an incorrect angle, are a problem with the OLS. Even moreso, obese people or persons with mobility impairments may be unable to complete the test. Officers usually do not take these variables into account when calculating the person's "normal" physical faculties. Fortunately, an attorney can point these items out to the jury, and the jury's assessment is the only one that counts.
Horizonal Gaze Nystagmus
In the HGN test, defendants must follow fixed points with their eyes without moving their heads. That fixed point is often a pen or a flashlight. Nystagmus is relatively easy for experienced test administrators to spot. If the defendant's pupil moves involuntarily at certain angles, that person almost always has nystagmus.
But intoxication is not the leading cause of nystagmus. In fact, it is not even close to the leading cause. Genetic defects, childhood injuries, and certain medications can all cause nystagmus. The condition is so mild that most people do not know they have it.
Furthermore, just as in the WAT, the test conditions are completely uncontrolled. Flashing squad car lights, dark skies, and other variables all affect test results.
Circumstantial DWI evidence is rather easy to challenge in court. For a free consultation with an experienced criminal defense attorney in Weatherford, contact Herreth Law. Convenient payment plans are available.