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Field Sobriety Tests

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Let’s imagine a scenario: You are in your car, it’s dark and cold outside. Suddenly you see flashing lights in your rear-view mirror; you pull to the side of the road, fumble for your license and insurance card, turn your radio off, and roll down your window. Officer Farva comes strolling up to greet you with a twisted smirk on his face.

Farva “Good evening, do you know why I stopped you”

You “No sir, I wasn’t speeding; was I?”

Farva “Well… a little while back I observed your car cross the yellow line. Have you had anything to drink tonight?”

You, having read my last blog “No sir, is there a problem or am I free to go?”

Farva “Well, I suspect that you have been drinking. Would you mind stepping out of the car on this cold and windy night to perform a series of tests? They are very difficult, will require you to listen to a complicated series of instructions, and even if you truly are sober I will mark each and every tiny mistake, so that I can later testify that you appeared to be drunk?

You “umm..”

Farva “I should add, there are many reasons you can fail these that are not related to being intoxicated. Also, many studies have shown these tests to be unreliable in determining whether or not you are intoxicated. And, I almost forgot to mention, refusing to take these does not give me probable cause to arrest you for DWI; I WILL arrest you if you refuse, but I’ll also arrest you after you take them, once I have gathered even more evidence to use against you in court!

You “What??”

Farva “One last thing.. I’m not very well trained in administering field sobriety tests, and the mistakes I make are probably going to skew the results even further, so passing these tests is pretty much out of the question.”

That conversation is never going to happen in real life. Police are not required to assist you in making informed decisions, but rather are trained to use tactics to encourage suspects to divulge as much evidence as possible so that they can build a stronger cases. Field Sobriety tests are a classic example.

Field sobriety tests are not required, and you cannot lose your license for refusing them, however, don’t get these confused with the breathalyzer, urine, saliva, or blood tests that the officer’s will ask you to consent to back at the station. You will know the difference between them because you will be under arrest for the latter, and will be read the Missouri Implied Consent Law before the officer requests you to submit to the breath, urine, saliva, or blood test. You should always request to speak with an attorney before making a decision. By law, ONLY IF YOU REQUEST TO SPEAK WITH AN ATTORNEY, the officer must give you 20 minutes to attempt to contact a DWI lawyer to advise you in making a decision on whether or not you should blow.

– Back to the “Standardized Field Sobriety Tests”, of SFST’s for short. There are three standard tests that officers are trained to administer when conducting an investigation of a suspected drunk driver. The first of these tests is the “Horizontal Gaze Nystagmus” test where the officer will ask the suspect to follow his finger with their eyes. The next test is the “Walk and Turn” test, where you walk the line. The third test that the officers give is the “One Leg Stand”. In the one leg stand test, the officer will ask you to stand on one leg and count until he tells you to stop.

Horizontal Gaze Nystagmus (HGN)

A “Nystagmus” is a an uncontrollable twitch, or jerkiness of your eyes. Officers will ask you to follow their finger so that they can look for any signs of intoxication based on a lack of “smooth pursuit” when looking from one direction to the other. Additionally the eyes will twitch uncontrollably when your eyes are concentrating on a target at maximum deviation. There is a third giveaway, whether or not the onset of the nystagmus begins at 45 degrees, but let’s save the math for your DWI attorney to handle!

Some things to consider about the HGN test:

  • There is no way to “pass this test” by concentrating or acting sober. The Nystagmus is an involuntary reaction that your eyes will exhibit if you have been drinking.
  • Even if you haven’t been drinking, validation studies have shown that up to 50% of completely sober people, with no medical conditions will show signs of a slight nystagmus at maximum deviation.
  • Many medical issues can cause you to show a “false positive”, such as certain types of brain damage, recent head trauma, inner ear infections, dizziness, or taking certain medications.
  • In addition to medical reasons, distractions such as moving lights, moving cars, wind, dust, and many other things can cause a nystagmus when the suspect is not under the influence of alcohol or drugs.

Keep in mind that the officer who is administering the test must do so in a very particular manner in order for the test to be valid. Although officers are trained to administer the test, it is very easy to make mistakes, and these mistakes can cause a false positive. This is especially troublesome, because the officer giving the test is the same person who is subjectively assessing whether or not you are showing signs of intoxication! And remember that this too is the same person who will be testifying in court that he administered the tests “by the book.”

Walk And Turn

The next test that officers give as part of the SFST’s is the 9-step walk and turn test. This test is given in order to test your balance, ability to follow instructions, and ability to do multiple things at once.

Before administering the test the officer is supposed to, but often does not, prequalify the area and the suspect to make sure administering this test would be appropriate. The location the test is to be administered must be:

  • Flat,
  • Dry,
  • Hard, and
  • Non-slippery

If all of the above conditions are met, the officer is also required to make sure there aren’t any disqualifying conditions such as whether the suspect is 50 or more pounds overweight, isn’t suffering from any leg or back injuries, and doesn’t have any inner ear infections. Officers are also trained to allow the suspect to remove their shoes if they have a two-inch heel, such as cowboy boots for men or high-heeled shoes for women. Again, officers rarely check for any of these things and each can cause you to perform poorly on the tests even if you are completely sober!

Now to the test: Basically the officer will instruct you to walk heel to toe for nine steps with your arms down at your sides in a straight line. When you reach the ninth step, you are instructed to pivot on your ninth step foot 180 degrees and walk heel to toe back to the starting point. This test actually begins before you take your first step! The officer will be looking for any of eight clues during this test:

  • Loss of balance during the instruction phase
  • Beginning the test before the instructions are given to do so
  • Stopping while walking
  • Failing on any step to touch your heel to your toe
  • Lifting your arms from your sides to balance yourself
  • Losing your balance on the turn, or turning in the wrong direction
  • Stepping off the line (which may be an imaginary line!)
  • Taking the wrong number of steps

Now, it doesn’t take a mathematician to realize that when you multiply all these possible mistakes over nine steps, the odds are against you, even if you are sober. In a National Highway Traffic Safety Administration-funded study from 1998, this test was given to 29 sober individuals, of which 27 FAILED!!! That is a failure rate of 93% for people who hadn’t been drinking!

One Leg Stand

The last of the SFST’s is the one-leg-stand. In this test the officer will ask the suspect to keep both legs straight, arms at your sides, and then lift one leg 6 inches off the ground and count until instructed to stop. This test is supposed to be administered for 30 seconds; the officer is supposed to instruct you to stop after the 30 seconds have passed.

The qualifications for this test are very similar to that of the Walk and Turn test, with many of the same concerns for the area in which to administer the test, and the physical abilities of the suspect.

During this test the officer is looking for four clues that you are intoxicated:

  • Any swaying while balancing
  • Using your arms to balance yourself
  • Hopping to keep balance, and
  • Putting your foot down due to loss of balance.

The Moral Of The Story

If you have been pulled over, especially if you have had anything to drink and you are asked to perform field sobriety tests, you are most likely going to do nothing but give the officer more evidence that will be used against you in your case. Even if you do very well on the physical ability / balance tests, there is no way to beat the horizontal gaze nystagmus test, and there are numerous factors that could cause you to show signs of a nystagmus even if you are well under the legal limit of .08 BAC. In most cases, the officer has already made a determination that he is going to arrest you before he even asks you to perform these tests, so there really is little chance that you are going to be able to “prove” your sobriety, and walk your way out of a DWI.

Author Bio


Matt Jett is the CEO and Managing Partner of Jett Legal, a Missouri personal injury law firm. With more than 10 years of
experience in personal injury, he has zealously represented clients in various legal matters, including car and truck
accidents, workers’ compensation, wrongful death, and other cases.

Matt received his Juris Doctor from the University of Missouri-Columbia School of Law and is a member of the Missouri
Bar Association. He has received numerous accolades for his work, including the Rising Stars distinction by Super Lawyers 2019-2022.

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