Do the Roadside DUI Tests Actually Measure Impaired Driving?

Everyday, average citizens all across the beautiful Commonwealth of Pennsylvania, are arrested and charged with DUI.  One of the most important pieces of evidence collected by the police and used by the prosecution in these cases are the Standardized Field Sobriety Tests (SFSTs).  Any conscientious defense lawyer, who specializes in DUI cases, recognizes the importance of these tests and the bearing they have on the outcome of the case.  Unfortunately, these tests and the way the police administer them,  have many flaws which bring into question the validity of the tests themselves and the results they produce.  This is the question we would like to address in this post, do the roadside DUI tests actually measure impaired driving?

Do the Roadside DUI Tests Actually Measure Impaired Driving?

After over eight years, 2,000 DUI cases, and after hosting and instructing at numerous seminars that certified lawyers in SFSTs, I can say that, at best, the SFSTs are a screening tool, and a faulty one at that.  The reasons why the roadside DUI tests are faulty are because they are very frequently administered incorrectly and they are based on very broad assumptions.

Improper Administration of the Roadside DUI Tests

The reason why the National Highway Traffic Safety Administration (NHTSA) standardized the field sobriety tests in the first place was to make sure the police were using tests that were scientifically backed.  This only holds true if the police exactly follow the prescribed procedure.  In fact,  NHTSA has mentioned very clearly in all of the police training manuals (in all caps) that:


So what is the reality on the ground? Lance Platt, a renowned expert and SFST instructor conducted a study on how police officers were administering these tests with citizens accused of drunk driving.  He reviewed thousands of actual videos of police officers testing accused drivers and concluded that 97% of the time, the police officer incorrectly administered at least one of the three tests.  This often times can result in false positives.

Even if the DUI tests were administered correctly, they are built on faulty assumptions.

The basic premise of these tests is that if there is no alcohol in the drivers system, they will be coordinated enough to pass these test.  This assumption is faulty because there are many things that can cause a person to become uncoordinated such as:

  • stress
  • fear of the police
  • confusion due to unfamiliar circumstances
  • illness
  • fatigue
  • prescription medication

and then there are some of us who are downright clumsy.  Then throw in the fact that you are ask to preform tasks that you never do in your routine life like walk heel to toe in a perfectly straight line and you can start to see why a person who is perfectly sober can fail these tests.  I have witnessed this many, many times in my career.

In summary, the Standardized Field Sobriety Tests are complex and need to be evaluated on  a case by case basis. If you our someone you know has been accused of DUI in PA then contact a DUI attorney who is  highly trained in complex DUI issues.

Justin McShane

PA DUI attorney Justin J. McShane is the President/CEO of The McShane Firm, LLC - Pennsylvania's top criminal law and DUI law firm. He is the highest rated DUI attorney in PA as rated by Justin McShane is a double Board certified attorney. He is the first and so far the only Pennsylvania attorney to achieve American Bar Association recognized board certification in DUI defense from the National College for DUI Defense, Inc. He is also a Board Certified Criminal Trial Advocate by the National Board of Trial Advocacy, a Pennsylvania Supreme Court Approved Agency.

3 responses to “Do the Roadside DUI Tests Actually Measure Impaired Driving?”

  • Even NHTSA admits that SFSTs do NOT measure impaired driving. That doesn’t stop officers and prosecutors from discussing “clues of impairment” when referring to SFSTs. If one actually reads the SFSTs manuals, no where do they describe “clues of impairment” because SFSTs do not measure driving impairment.
    The following is copied from the 1998 San Diego Study, pages 27 and 28.
    Many individuals, including some judges, believe that the purpose of a field sobriety test is to measure driving impairment. For this reason, they tend to expect tests to possess “face validity,” that is, tests that appear to be related to actual driving tasks. Tests of physical and cognitive abilities, such as balance, reaction time, and information processing, have face validity, to varying degrees, based on the involvement of these abilities in driving tasks; that is, the tests seem to be relevant “on the face of it.” Horizontal gaze nystagmus lacks face validity because it does not appear to be linked to the requirements of driving a motor vehicle. The reasoning is correct, but it is based on the incorrect assumption that field sobriety tests are designed to measure driving impairment.
    Driving a motor vehicle is a very complex activity that involves a wide variety of tasks and operator capabilities. It is unlikely that complex human performance, such as that required to safely drive an automobile, can be measured at roadside.

  • Mr. Brown,
    Thank you for both the interest that you have shown in reading my original post, but also in taking the time in posting an insightful comment.
    Not only are you wholly correct, but the proverbial rabbit hole goes even deeper as I will write in my next post.
    What I did not write in my next post and what fits nicely as a follow up to your comments concerns the deposition that was taken of Dr. Burns by my great friend Bruce Kapsack and also Hudson Bair of San Fransico on April 17, 1998. In this deposition Dr. Burns provided truthful testimony under oath as follows:
    Q: Now, these standardized tests were developed as an aid for officers to make an initial determination in the field as to initially whether or not the person had a blood alcohol level that was over .1; correct?
    That was the initial —
    A (By Burns): That’s correct, .1 or above.
    Q: These tests [the 3 Standardized Field Sobriety Tests], in and of themselves, don’t state whether the person is able to drive the vehicle. In other words, these tests show there is a likelihood that someone is over .1, and since the medical community is pretty much in agreement that over .1 means you’re not capable of operating a motor vehicle reasonably under the law, at least, the tests can therefore be used for that, but directly, the tests don’t show the ability or inability to operate a motor vehicle; correct?
    A (by Burns): Correct. What you’re asking is, are these tests of driving? They are not. If they were tests of driving, they would be field driving tests. I can elaborate on the reasons and everything behind that if you want, but they are not tests of driving. They are tests of sobriety. There’s a whole series of literature that tests alcohol and driving schools.
    Q: That’s the missing link, so to speak. The sobriety tests will tell you the probable level of
    alcohol, or at least the probable minimal level of
    alcohol, and then you go to the literature or the expert or the doctor to say what effect that level of alcohol will have on a person’s mental and physical abilities regarding driving?
    A (by Burns): Well, the research over the years is what led the legislators to choose the levels that they did. And as the research accumulates, those levels keep coming down. The officer is not charged with making a decision about driving skills at roadside. He couldn’t. There’s no way you can judge somebody in five minutes at roadside that you never saw before to make a decision about their driving skills. What he is charged with doing is making a
    judgment about their sobriety or presence of alcohol
    or impairment by alcohol, if you will.
    Also very suspect is the fact that Dr. Marcelline Burns by her formal education is a research psychologist.

  • Interesting article. I recently was in an accident. After the accident, I felt shock and panic – my vehicle was totaled, and I wasn’t sure if I was in a dream or what.
    When the police arrived, they took my signs of nervousness (I was so nervous, I dropped a cigarette, fumbled around to get it, and basically was shaking the entire time) as signs of “impairment.”

Leave a Reply

Your email address will not be published. Required fields are marked *