Standardized field sobriety tests

At some point after stopping a driver for a suspected DUI, the officer will try to have the driver perform  so called “field sobriety tests.”  Please note: there are field sobriety tests and standardized field sobriety tests.  The National Highway Traffic and Safety Administration (NHTSA) explains that standardized field sobriety tests are called “standardized” because they must be administered in the same fashion each time; standardized clues are used to access the driver’s performance on the tests; and standardized criteria are used to interpret the driver’s performance on the tests.

The National Highway Traffic and Safety Administration (NHTSA) conducted research to validate research concerning several field sobriety tests.  Please note: all information referenced to “NHTSA” is from their February 2006 Edition, DWI Detection and Standardized Field Sobriety Testing.

I am using the language from NHTSA  and DWI Detection and Standardized Field Sobriety Testing, because law enforcement is trained with this information and book.  I want you, the reader, to see what law enforcement if being told about DUI investigations, because you have more likely than not, been subjected to a DUI related investigation conducted in part based on techniques and procedures attributed to NHTSA.

NHTSA directs the officer to administer three scientifically validated field sobriety tests.  Based on the performance on these tests, as well as the observations made concerning the driving and face to face contact, the officer must then decide whether to arrest the driver for a suspected DUI.

The field sobriety tests, per NHTSA at page VII-4, are designed to focus on the driver’s abilities to make divided attention related decisions necessary for safe driving that involve:

information processing

short term memory

judgment and decision making


steady and sure reactions

clear vision

small muscle control

coordination of limbs

NHTSA requires at page VII-4 that “simplicity is the key to divided attention field sobriety testing.  It is not enough to select a test that just divides the subject’s attention. The test must also be one that is reasonably simple for the average person to perform when sober. Tests that are difficult for a sober person to perform have little or no evidentiary value.” (Emphasis added.).

Research, per the NHTSA, shows that when three of the field sobriety tests are administered correctly and in a standardized manner, they were highly accurate in distinguishing blood level alcohol concentration above .10%:  Those three tests are the following:

Horizontal gaze nystagmus (abbreviated “HGN”)

Walk and Turn (abbreviated “WAT”)

One leg Stand (abbreviated “OLS”)

NHTSA analyzed data at VIII-1 and found that

HGN, by itself, was 77% accurate in distinguishing blood level alcohol concentration above .10%:

WAT, by itself, was 68% accurate in distinguishing blood level alcohol concentration above .10%:

OLS, by itself, was 65% accurate in distinguishing blood level alcohol concentration above .10%:

by combining HGN and WAT an 80% rate of accuracy can be achieved

These three field sobriety tests, HGN, WAT, and OLS are called standardized field sobriety tests. “Standardized” means that the tests are administered and interpreted in the same way each and every time.

NHTSA at page VIII-2 claims that two validation tests showed that the use of all three tests, HGN, WAT, and OLS, were highly successful in identifying persons whose blood level alcohol was above .10%.  The first of the two tests, a 1995 Colorado validation study, showed that correct arrest decisions were made 93% of the time based on using all three tests (HGN, WAT, and OLS).  The second study, a 1997 Florida validation study, determined that 95% of the arrests were made correctly using all three tests, HGN, WAT and OLS.

Unlike the other two tests finding reliability for identifying BAC of over .10%, a 1998 San Diego test at page VIII-2 determined that correct arrest decisions were made 91% of the time based on the use of all three standardized field sobriety tests for a blood level alcohol of .08% or more.

Please remember, though, that despite the aura of scientific validity, these tests can be refuted!  Police routinely fail to administer and score the tests correctly.

In summary, NHTSA warns at Page VIII-19 that the validation (percentages of persons likely to over .10% BAC or more) involving the three tests applies only when





This is critical: if the police do not perform any of the three standardized tests completely correctly, that test result is compromised, per NHTSA.  (Page VIII-19).

The results of these so called field sobriety tests can be attacked and refuted!  Find out how you can defend against your DUI arrest!  You should contact an experienced DUI lawyer Mark Blair for a free, informative and confidential consultation to develop your DUI defense!  Mark has represented thousands of persons who have suffered a DUI arrest.  Please call Mark Blair at (408) 295-4343, (650) 344-4343, (510) 845-4343, (415) 664-4343 (925) 935-4343 or (707) 252-4343.

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