Why a Failed Field Sobriety Test Might Not Mean a DUI

When people learn I am a DUI attorney, they often ask me: “Do you really go to jail if you can’t say the alphabet backwards?” Field sobriety tests like this one are often portrayed on TV as impossible tests, designed for failure.   While this test and many others, including counting on your fingers, have not been linked to the safe operation of a motor vehicle, it is important to know that 3 of them have been scientifically correlated to an elevated blood alcohol concentration.  These are known as the “standardized field sobriety tests.”  However, like any scientific test, they must be properly administered and scored in order to be accurate. 

Therefore, if you failed a field sobriety test and are facing DUI charges, not all hope is lost.  But, it’s not that simple.  Let’s look at what these tests are, how they are designed and how I’ve been able to successfully dismiss DUI cases when field sobriety tests are poorly administered.

What are the three standardized field sobriety tests?


The three standardized field sobriety tests are horizontal gaze nystagmus (HGN), one leg stand (OLS), and walk and turn (WAT).   

HGN: checks the eyes for involuntary jerking when following a pen or similar object 

OLS: checks for balance as the driver raises one foot off the ground for 30 seconds  

WAT: checks for balance as the driver walks back and forth on an imaginary straight line

How do you fail these field sobriety tests?


When police conduct the tests, they are looking for a specific set of “clues” that indicate failure as listed by the National Highway Traffic Safety Administration (NHTSA).  These clues suggest the driver is above California’s legal limit of .08 blood alcohol concentration.   

For example, the four possible clues on the one leg stand are:

1. putting foot down
2. hopping
3. raising arms to balance
4. swaying

According to NHTSA, if someone presents with 2 or more of these clues on the one leg stand, this is considered a failure as there is an 83% chance their blood alcohol level is a .08 or higher at the time of the test.

What happens if you “fail” a field sobriety test?


If you “fail” a field sobriety test, you may be arrested for DUI.  Once arrested, you should contact a DUI attorney iwithin the next 24 hours. The DUI attorney will evaluate whether police properly administered the test or whether a medical or physical condition could explain the failure.

What are problems with field sobriety tests?


The correlation between field sobriety test clues and BAC is not perfect.  Sometimes the officer does not know how to score clues.  More importantly, sometimes the officer does not give the proper instructions established by NHTSA when conducting the test.  According to NHTSA, there are 10 steps an officer should follow when conducting the eye jerking test), 13 steps for the one leg stand, and 17 steps for the walk and turn.

I know from my own experience, when I conducted field sobriety tests on subjects who had been in a controlled drinking environment beforehand, that when I didn’t follow the proper steps when conducting each test, my test subjects often failed.

Examples of failed field sobriety tests that did not lead to DUI

Example 1: 1-80 and Elm Street in Auburn DUI – Walk and Turn Test

Here’s an example of when improper instructions from police can lead to field sobriety test failure.  Last month, I represented a client arrested for DUI on I-80 and Elm Street in Auburn.  The police report said he “failed” the walk and turn test by scoring the following clues: 1) missing heel-to-toe, and 2) raising arms to balance.  According to NHTSA, this means there was a 79% chance he was at or above .08 BAC at the time of the test.  

But, when I looked at the body camera, I noticed that of the 17 steps for the walk and turn this officer failed to follow 2 important steps related to instruction.  He failed to instruct my client to 1) look at his feet when walking; and 2) keep his arms at his sides.  

At a DMV hearing, we reinstated his license with full driving privileges. In part, we argued that the officer’s failure to follow these steps and properly instruct my client set him up for failure. How can he be scored a clue for raising his arms when the officer failed to tell him to keep his arms at his sides? How can he be scored a clue for missing heel-to-toe on an imaginary line when the officer failed to instruct him to look at his feet when walking?  

Example 2: I-80 at Sierra College Blvd in Rocklin –  Eye Jerking Test

A few months ago, I represented a client arrested for DUI on eastbound I-80 near Sierra College Blvd in Rocklin, just after he left Roseville.  The only field sobriety test police performed prior to his arrest was horizontal gaze nystagmus.  However, at a pre-trial motion-to-suppress hearing, the officer admitted under my cross-examination that he did not check my client’s eyes for “resting nystagmus” when conducting the test.  Checking for resting nystagmus, which is a medical condition that causes the eyes to naturally jerk when looking straight ahead, is one of the ten steps an officer must follow when conducting the horizontal gaze nystagmus test.  This is because, according to NHTSA, anyone who has resting nystagmus can “fail” that test regardless of whether they consumed alcohol, because their eyes will jerk when following a pen.   After I presented this argument to the judge at the close of testimony, the DA dismissed the case.

Can a sober person fail a field sobriety test?

This last example also shows how someone can fail a field sobriety test even if they had nothing to drink.  This is because of certain medical or physical conditions.  When conducting horizontal gaze nystagmus for instance, the officer must not only check the driver for the medical condition of resting nystagmus, but also equal pupil size and equal tracking. Equal tracking means that both eyes move at the same time when following an object. A driver with these medical conditions will usually present clues from this test even if he is sober.  

Similarly, a driver with certain physical conditions will often present clues on the balancing tests of one leg stand and walk and turn even if he is sober or under a .08 BAC.  NHTSA specifically instructs that drivers who are older, overweight, or have knee, back, or inner ear problems will usually have trouble with the tests regardless of sobriety.  Therefore, it is important for a driver to alert the officer of any medical or physical issue he or she may have prior to performing field sobriety tests.

How I developed my knowledge of field sobriety tests

Last year, I attended and passed the same 3-day course that officers must pass before conducting field sobriety tests in a DUI investigation.  The information from that course is of utmost importance for DUI attorneys because almost every DUI charge comes after someone has “failed” field sobriety tests.

DUI conviction isn’t certain when you fail a field sobriety test

If you have been charged for DUI based on “failing” field sobriety tests, it is important to contact a DUI attorney to evaluate whether the officers properly conducted each test, or if a condition may explain the “failure.”  At the Cohen Defense Group, we are well-versed in these issues and are available for a free consultation.  

Related: DUI Conviction Isn’t Certain When You Have a Blood Alcohol Level of .10 After Driving.

Related: Can You Refuse a Breathalyzer After Being Arrested for DUI?

About Zachary Merliss

Zachary Merliss HeadshotZach Merliss focuses his practice on DUI law in Placer County. He teaches the “legal aspects” lecture at a First Offense DUI School in Auburn, and successfully completed the 3-day Standardized Field Sobriety Test Academy, which is the same course police must pass before conducting a DUI investigation. He has litigated dozens of DMV hearings, DUI trials, and motions to suppress evidence. During his time at the Cohen Defense Group, he has worked hard for clients to obtain reduced sentences and dismissals.