Delaware Lawyer Telling the Truth About DUI Field Sobriety Tests

You Do Not Have To Take the Test

Many people are not aware that field sobriety tests are totally voluntary. The police do not tell the motorist at the scene of the arrest that they have every right to refuse to take the tests.

With FST testing, there is little doubt that law enforcement makes the final call as to whether or not the person has passed or failed. Law enforcement often believes a person to be intoxicated if they ask him or her to perform field sobriety tests.

The observation of the police officer may indeed be faulty or biased, and yet in Delaware they make a report of the arrest which by its very title indicates bias and prejudice. The report is termed the AIR report, or "alcohol influence report." Without a skilled DUI attorney, even good faith errors by the officer can result in a DUI conviction.

Challenging Field Sobriety Test Validity

In the scientific community, validity refers to a test's ability to do what its intended purpose is, in this case, for the FSTS to measure impairment. One of the conclusions found in the 1977 federal study is that the officer's ability to determine BACs over the then existing threshold of .10 was only 26% better than had they just simply guessed. Another way of putting it, statistically speaking, is that the combined error in predicting BAC levels using the HGN, Walk the line, and Leg Raise tests is 74% as large as it would be by mere chance. This is what the data revealed.

In Delaware it is common for judges, prosecutors and even defense attorneys to talk about the NHTSA studies being about 80% accurate. They attempt to bolster the credibility of the field tests by repeating this statistic during DUI trials. A white lie is repeated again and again until it receives respectability. As a wise man once said, there are lies, damn lies and then there are statistics.

They have not read the actual studies, and as members of the law enforcement community, do they seriously want to?

Here are the real statistics. In the 1981 NHSTA study, after making test observations in the laboratory and not at roadside, the officers were asked to estimate whether or not the subject was impaired. Test validity of a study often depends upon heterogeneity; in other words, an even sampling of the subjects at each level. The 1981 study involved 296 subjects. While some subjects were dosed around the legal limit - that is to say, they were intended to be "close calls," most of the subjects were dosed at the extremes.

97 people were dosed at 0% alcohol, that is 32%
102 people were dosed at .05% alcohol, that is 34%
33 people were dosed at .15% alcohol, that is 11%

Here, of the 296 subjects in the study, you can see that 199 were at a .0% or .05% alcohol dosage, or over the .15% dosage. I would strongly suggest that over 2/3 of the subjects were designed to be almost "gimmes" for the police because their BAC were at the extremes. So how hard was it for the officers to make the correct guess?

Even so, evidently it was still pretty tough. Shockingly, the officers still had a false alarm rate for the entire subject test body of 32%, (!) even when over 2/3 of the people were essentially freebies. Statistically speaking it is almost nonsense to speak of the NHTSA tests as resulting in an accuracy or prediction rate of 80% if so many of the subjects were designed to be freebies for the police. Yet all we seem to hear about is the 80% predictability of the NHTSA FSTs. I strongly disagree.

Why Are Field Sobriety Tests So Unreliable?

The sources of Field Test Predictability errors are manifold: improper training or retraining of the officers, poor standardization of test instructions, poor administration and poor scoring of tests results, and so forth. The biggest problem, however, may be with the FST tests themselves. To the law enforcement officer who has demonstrated the tests many times, the motor sequences may seem easy. It may also be that to the casual observer the tests are easy to perform. Yet when an untrained individual actually performs the tests, the difficulty in performing the tests to an acceptable level may become quite apparent.

The inescapable conclusion for any good DUI lawyer is that the federally sanctioned NHTSA sobriety tests are designed for failure for quite a few of us "regular" individuals. Therefore, do not be discouraged if you believe you failed the tests. Appropriate cross-examination of the arresting officer is vital to your defense.

Kevin P. O'Neill, Attorney at Law • Wilmington, Delaware • Contact Me