Field Sobriety Tests (FSTs) are the roadside examinations administered by the police officer in investigating whether you were operating your vehicle under the influence of alcohol. Field sobriety tests are standardized tests and were developed and sponsored by the National Highway Traffic Safety Administration (NHTSA). The standardized field sobriety tests, if given in a prescribed manner, under a standardized setting, supposedly demonstrate validated indicators or cues of a person's impairment. When the tests are administered in the manner detailed by the NHTSA and an officer observes these cues, it allows him to establish probable cause to believe an operator is impaired and arrest that person for OUI. Many times the FSTs are administered incorrectly, in an inappropriate setting or to an inappropriate candidate. Even if administered correctly, according to the NHTSA, there are large degrees of unreliability applicable to these tests, as much as 35%. According to the National Highway Traffic Safety Administration, if any of the standardized criteria for the administration of the tests is compromised, the validity of the test results is diminished beyond the already high degrees of unreliability. Additionally the "scoring" of the test perfomances by police officers is highly subjective. There are very few objective findings in field sobriety testing. The scoring format is negative scoring. The subject does not get credit for how much of the test he or she does correctly, but rather how many things are done incorrectly. The three primary standardized field sobriety tests are:

Horizontal Gaze Nystagmus

In the performance of this test, an officer asks a suspect to following a pen or small flashlight, tracking left to right with his eyes. A person's eyeball jerking (nystagmus) is magnified by the amount of impairment due to alcohol. There are, however a large number of causes of nystagmus other than alcohol. This test is regularly deemed inadmissible in Massachusetts as the officer lacks the qualifications to interpret the eye movements to properly evaluate this test. Despite its non-evidentiary use, police officers conducting tests roadside regularly utilize this test in the formation of probable cause to place a suspect under arrest for OUI.

Back to top

Nine-Step Walk and Turn

The nine-step walk and turn test is a divided attention examination. One part of the test is the cognitive phase. The officer is conducting observations of the operator's ability to understand and follow instructions during the course of this phase of the test. During this time, the officer is verbally instructing and physically demonstrating how he wishes this test to be performed. The operator is advised to stand still, feet together, hands at his side during the performance of the instruction phase. He is also instructed not to start the test until all of the instruction and demonstration is complete. The officer will typically make and record observations of an operator during this phase. The second phase is the performance of the test. What is required in the physical performance of the test is that the subject walk on a straight line, one foot in front of the other, touching heel to toe, keeping his arms to his side, counting the steps out loud. The subject is required to take nine steps out, articulate a turn at the end and take nine steps back in the same manner. During the performance of this test, the officer is watching for eight clues of impairment:

  1. Loses balance during instruction
  2. Starts test before instructions are finished
  3. Stops during performance of test to steady self
  4. Fails to touch heel to toe
  5. Steps off of line
  6. Uses arms for balance
  7. Loses balance or turns improperly
  8. Takes the wrong number of steps

If a suspect demonstrates two of these eight clues at any time during the performance of this test, the subject is deemed to have failed this test. This test supposedly demonstrates a 68 percent reliability that the subject is under the influence of alcohol and has a BAC of .10 (now .08) or more. In the proper administration of the 9 Step Walk and Turn Test there are 93 opportunities for the subject to demonstrate a clue. A subject could successfully complete 91 of the 93 opportunities to demonstrate a clue and still have the test deemed to be a failure.

Back to top

One Leg Stand Test

Like the nine-step walk and turn test, the one leg stand test also is a divided attention test, cognitive and performance. During the instruction stage, the suspect is required to stand with his feet together and his arms at his side. The officer should verbally instruct and demonstrate the performance of this test for the subject. The performance stage of this test requires that the subject stands with one foot of their choice approximately 6 inches off the ground, straight out in front of them and counts out loud by thousands for 30 seconds. The suspect is advised not to hop on the one foot or to use his arms for balance. During this test, the officer is trained to observe for four clues of impairment:

  1. Swaying while balancing
  2. Using arms for balance
  3. Hopping to maintain balance
  4. Putting foot down before completion of test

If an officer observes two or more of the above clues, this test supposedly demonstrates a 65 percent reliability that the subject has a blood alcohol content of .10 (now .08) or more. The One Leg Stand Test has 151 opportunities for a subject to demonstrate a clue. 149 out of 151 clue opportunities of the test could be successfully completed and it would still be a failure.

Back to top


There are certain conditions, under which the tests should be administered, as required by the NHTSA. The tests are to be administered on a hard, dry, clean, non-slippery, level surface in a well-lighted area. Tests that are administered in less than standardized conditions diminish the already marginal results, which an officer might obtain. Additionally, the physical condition of the Defendant can afffect the test performance. Persons who have problems with their neck, back, legs or feet can have a difficult time doing these tests successfully to the degree necessary. Other problems like ADD, ADHD or Anxiety can greatly impair a persons ability to do these tests. The tests that are mentioned above are the only tests that are validated for use by an officer in detecting intoxication in an operator. Oftentimes you will see or hear about tests such as touching finger to nose, picking up coins, and counting backwards being utilized by officers as field sobriety tests. There is no scientific validation for these tests and they offer little or no documented reliability for the officer to accurately detect impairment. Remember, if any element of the standardized field sobriety test is altered or compromised, then the validity and reliability of the test is compromised. These compromises work in your favor in court.

Back to top

Can I refuse the Tests?

In Massachusetts, an operator has a right to refuse to perform field sobriety tests. By performing field sobriety tests, you are only providing evidence to the officer in forming his OUI case against you. As noted above, these tests have to be perfomed almost 100% correctly to be considered a "pass". Many officers don't understand the FST's criteria or remember them from the police academy. Oftentimes it appears that the operator was already going to be arrested before the tests were even administered, and they were administered so the officer could record some observations for his report. The roadside field sobriety tests are also almost never recorded by the poilce. This creates a situation at trial where it would be your word against the police officer's word if you disagreed with his description of your performance on the tests. In the typical administration of field sobriety tests, a police officer will not describe to the subject the criteria he is looking for in the performance of this test. The officer typically will not describe to the subject the various clues he is looking for. The officer typically will not describe the number of clues necessary to formulate the failure of the test by the operator. In a typical stop, the officer will ask the operator to perform several field sobriety tests. At the conclusion of those tests, the officer will inform the operator that he is placing the subject under arrest. Prior to advising the operator they are under arrest, the officer will have virtually no discussion with the operator about the performance of the tests. It is not uncommon to have persons arrested for OUI to state that they did well on the FSTs only to see a completely different description of their performance as described by the officer in his arrest report.

Remember, everything you say and everything you do can and will be used against you in a court of law. Be smart and protect yourself.

Back to top


This article is intended as an overview of basic field sobriety tests administered by local police departments as instructed by the NHTSA. The foregoing is provided for information purposes only. For a more encompassing discussion of field sobriety testing, you should consult in person with a qualified criminal defense lawyer.

Back to top

738 Main Street                         Route 228                             Hingham, MA 02043

The Torney Bldg.,
15 Foster Street,
Quincy, MA 02169

54 Samoset Road,
Route 44,
Plymouth, MA 02360

Phone: 866.770.1100