Field Sobriety Tests In Arizona

The three most common field sobriety tests in Arizona (“FSTs”) are the Horizontal Gaze Nystagmus test, the Walk and Turn test, and the One-Leg Stand test.  These three tests are standardized by the National Highway Traffic Safety Administration (“NHTSA”), which means they must be conducted the same way every time to be valid.

  • Horizontal Gaze Nystagmus (“HGN”):  This is an eye test in which the officer has the suspect follow a stimulus (usually a pen) with his eyes while keeping his head still.  If the suspect can’t keep his head still or follow the stimulus with his eyes, the officer will usually note this as evidence of impairment.  The officer is looking for nystagmus, which is an involuntary jerking of the eyeball.  There is always some level of nystagmus in the human eye, but alcohol or drug use can exaggerate the nystagmus so that it is detectible.  There many other things, aside from alcohol or illegal drugs, that can exaggerate nystagmus.
  • Walk and Turn:  This is a test in which the officer has the suspect walk in a straight line, heel-to-toe, nine steps down the line and nine steps back without stopping.  The suspect is supposed to keep his arms at his sides, watch his feet at all times, and count his steps out loud.  After the first nine steps, the suspect is required to turn using a series of small steps.  While many officers use an “imaginary line” for this test, NHTSA requires that there there be an actual line.  NHTSA provides officers with certain clues to look for on this test, but only some of these clues are validated (supported by studies).  The validated clues are: (1) cannot keep balance while listening to instructions, (2) starts before instructions are finished, (3) stops while walking, (4) does not touch heel-to-toe, (5) steps off the line, (6) uses arms for balance, (7) improper turn, and (8) incorrect number of steps.  According to NHTSA, research has shown that people over 65 years-old and people who have back, leg, or inner ear problems have had difficulty with this test even when sober.
  • One-Leg Stand:  This is a test in which the officer has the suspect stand on one leg, with his arms at his sides, while counting out loud.  The suspects other foot is supposed to remain about six inches off of the ground.  NHTSA directs officers to look for four validated clues: (1) swaying while balancing, (2) using arms for balance, (3) hopping, and (4) puts foot down.  Interestingly, the NHTSA manual directs officers not to look at the suspects feet for officer safety reasons.  According to NHTSA, research has shown that people over 65 years-old, people who have back, leg, or inner ear problems, and people who are at least 50 pounds overweight have had difficulty with this test even when sober.

There are other field sobriety tests that are sometimes used by certain law enforcement agencies and/or officers in Arizona.  These include the Modified Romberg and the Finger-to-Nose test.  These tests are not standardized or validated by NHTSA, but that doesn’t prevent officers from using them or testify about them in court.

  • Modified Romberg:  The suspect must stand with his feet together, his head tipped back, his arms at his sides, and his eyes closed for 45 seconds.  Officers are basically looking for one thing — swaying.
  • Finger-to-Nose:  The suspect must stand with his eyes closed and his arms out to his sides.  He must then alternate between using his left and right index fingers to touch his nose.  If the suspect misses his nose or does not use the tip of his index finger, officers will consider this as evidence of impairment.  As always, officers are also looking for swaying and problems with balance.

It is rare to see a DUI case in Tucson where police reports indicate that the "suspect" passed any of these tests. When video footage of the tests exists (most commonly police body camera footage), the tests often look better on video than what the officers describe in their reports. Video can also reveal important mistakes made by officers during a DUI investigation, so it is important that you demand that the State disclose any video that exists.

The tests listed above are not the only tests officers give during a DUI investigation. In fact, you are constantly being tested throughout your encounter with the police. The NHTSA manual described various types of driving behavior before that it claims indicates possible impairment. NHTSA also instructs officers to present suspects with divided attention tasks upon initial contact. For example, NHTSA says officers should ask the driver to produce their license, registration, and insurance documents and, while the driver is retrieving these items, continue to ask questions about other things, like where they are coming from, where they are going....

Police are watching the way you find and handle your documents, how you get out of your car, how you are answering their questions, how you are speaking, how you smell, whether you are emotional or moody, how you stand, and how you move. Although less formal than the field sobriety tests outlined above, these are all tests that are used to determine whether you are impaired.

As you can see, a DUI investigation begins before the traffic stop and continues throughout your encounter with the police. You are constantly being testing and observed in order to develop probable cause for a DUI arrest and develop evidence that can be presented in court. An officer's determinations and interpretations are not always correct, but you need to know what to look for to find and demonstrate his or her errors.

If you are facing DUI charges in Arizona, it is critical that you are represented by an experienced DUI attorney who knows this area of the law. At Leonardo Law Offices, we are experienced in handling felony and misdemeanor DUI cases, including extreme and super-extreme DUI charges, and have had good results. For a free assessment of your case, call our Tucson, Arizona office at (520) 314-4125 or contact us online.


Consult the following links for more information about Arizona Criminal and DUI laws, as well as local court information:

Arizona Revised Statutes

Tucson City Court

Pima County Justice Court

Pima County Superior Court

Maricopa County Superior Court

Pinal County Courts

Santa Cruz County Courts

BAC Calculator

Other Links