"Field Sobriety Tests" in Nevada DUI cases
Explained by Las Vegas Criminal Defense Attorneys

Nevada police who suspect someone of driving impaired will ask that person to perform DUI field sobriety tests ("FST's"). FST's consist of three psychophysical exercises that are meant to help officers identify whether the person in drunk or high ... but the tests are not always reliable.

Sometimes police improperly administer FST's. Furthermore a poor FST performance can result from non-intoxicant causes such as illness. A skilled Nevada criminal defense attorney may be able to show that a failing FST score is inaccurate and that any DUI charges should be dropped.

This article explains how FST's work in Nevada DUI cases. Continue reading to learn what the tests comprise of and how Nevada attorneys challenge them as evidence.


What are field sobriety tests in Nevada DUI cases?

Field sobriety tests (FST's) are pseudo-scientific exercises that police ask DUI suspects to do. How the suspects perform the FST's and follow instructions is meant to aid police in detecting whether they were indeed committing the Nevada crime of driving under the influence of alcohol or drugs.

When are FST's administered in Nevada DUI cases?

Shortly after the police arrive at a suspected DUI scene...

First the cop will ask the suspect some cognition-testing questions such asking for his/her license and registration. Meanwhile the cop will note if the suspect smells of alcohol or displays intoxicated features such as bloodshot and glassy eyes. At that point the cop will ask the suspect to perform the field sobriety tests.


What are FST's like in Nevada DUI cases?

Nevada FST's consist of three separates tests:

  1. Horizontal Gaze Nystagmus,
  2. Walk-and-Turn, and
  3. One-Legged-Stand

1) Horizontal Gaze Nystagmus (HGN):

The HGN is an eye-test where the suspect is instructed to keep his/her eyes fixed on the cop's penlight (or other object) as he/she moves it from side to side. In the meantime the cop is looking at the suspect's pupils for involuntary jerking ... called "nystagmus" ... which can be a sign of intoxication.

Specifically, the cop is checking for three "clues" of intoxication in each eye:

  1. "Lack of smooth pursuit." This is where the pupil spontaneously jerks while following the cop's penlight. Theoretically, a sober person's eyes would move smoothly.
  2. "Distinct nystagmus at maximum deviation." For four seconds the cop holds the penlight very far to the side so the suspect's pupils are at maximum deviation. If the pupils bounce, it may be a sign of intoxication.
  3. "Onset prior to forty-five degrees." As the officer moves the penlight back and forth, the officer is studying whether the suspect's pupils jerk prior to the penlight being at a forty-five degree angle away from the suspect's face. If it does, it could be a sign of intoxication.

During the HGN, the officer is tallying how many "clues" each eye is exhibiting. The maximum number of clues a suspect can show is six (three for each eye). Showing four or more clues is a failing score. For more information on Nevada horizontal gaze nystagmus tests, see our article on Nevada horizontal gaze nystagmus tests.

2) Walk-and-Turn:

The walk-and-turn test is where the suspect is instructed to take nine steps heal-to-toe back and forth. In addition, the suspect has to keep one foot on the ground as he/she pivots around during the halfway point. Furthermore, the suspect has to count the numbers aloud.

In the meantime, the cop is looking for eight "clues" of intoxication:

  1. The suspect cannot keep balanced while the cop is giving him/her instructions.
  2. The suspect starts to walk before the cop finishes giving the instructions.
  3. The suspect pauses during the walk to steady him/herself. (Note that walking slowly is okay as long as there is no stopping.)
  4. The suspect is not walking heal-to-toe.
  5. The suspect steps out of line.
  6. The suspect uses his/her arms to balance.
  7. The suspect loses his/her balance while doing the turn.
  8. The suspect takes more or less than the nine steps required in each direction.

Showing two or more clues during the walk-and-turn test is a failing score. For more information on Nevada walk and turn tests, see our article on the Nevada walk and turn test.

3) One-legged stand.

For the one-legged stand test the suspect has to stand in place on one leg while keeping the other leg extended forward about six inches off the ground. Simultaneously, the suspect has to count aloud to thirty saying "One one-thousand, two one-thousand, three one-thousand..." etc.

Meanwhile, the cop is looking out for the following four "clues" of intoxication:

  1. The suspect hops.
  2. The suspect puts a foot down.
  3. The suspect uses arms for balance.
  4. The suspect sways while balancing.

Exhibiting two or more clues in the one-legged-stand test is a failing score. See our article on the Nevada one leg stand test.


Can Nevada DUI suspects refuse to perform FST's?

Yes. They are not mandatory. But then the cops will usually construe the refusal as a sign of guilt and arrest them for DUI anyway.

How accurate are the FST's in Nevada DUI cases?

Not very. Statistically, one out of five people who test positive for DUI in FST's is not under the influence of drugs or alcohol. "False positives" can be caused by various circumstances such as:

  • uneven surface for the walk-and-turn and one-legged stand tests
  • bad lighting for the officer to observe the DUI suspect
  • disruptive distractions such as traffic, bright lights, and spectators
  • footwear unsuitable for the walk-and-turn and one-legged stand tests
  • fatigue, illness, injury, or anxiety suffered by the DUI suspect
  • windy or rainy weather
  • intimidation by the cop
  • prescribed medication that causes the DUI suspect to lose coordination or for his/her eyes to display nystagmus
  • physical limitations of the DUI suspect such as old age, obesity, or other conditions that interfere with coordination

In addition maybe the cop did a poor job of communicating instructions to the DUI suspect. Or perhaps the cop was inherently biased against the suspect. In sum, there are several factors that can cause a sober person to exhibit false clues during FST's in Nevada.

What happens after DUI suspects perform FST's in Nevada?

If the DUI suspect does not pass the field sobriety tests, the cop will probably ask the suspect to submit to a preliminary breath test (PBT) and then arrest him/her for DUI. The suspect will then be booked and given a Nevada DUI breath test or a
Nevada DUI blood test.

Usually DUI suspects who pass the field sobriety tests are released at the scene. Depending on the reason they were pulled over, they may be given a non-intoxicant related traffic citation in Nevada such as speeding.

Note that whether a person is arrested for DUI is up to the cop's discretion. In some cases the police may believe there is probable cause to believe a driver is under the influence even if he/she passes the FST's and preliminary breath test.


How do defense attorneys show that FST results are inaccurate?

If prosecutors press DUI charges, the defense attorney would conduct a thorough investigation into the night of the arrest. They will seek out surveillance video or eyewitnesses to the field sobriety tests. And they will aggressively cross-examine the officers during the Nevada DMV Hearing, which is like a mini-trial to contest the defendant's license suspension.

Any evidence the defense attorneys find of false FST results serves as invaluable bargaining chips when negotiating with the prosecutor to reduce the Nevada DUI charges to reckless driving or even a full dismissal. And if the case goes to trial, this evidence may make it impossible for the prosecutor to prove guilt beyond a reasonable doubt.


Who came up with FST's in Nevada DUI cases?

The National Highway Traffic Safety Administration (NHTSA). it is a federal government agency meant to promote and safeguard highway safety. Here is the official NHTSA overview of FTS's.


Arrested for DUI? Call a lawyer ....


If you have been accused of driving while impaired, call our Las Vegas Nevada DUI attorneys at 702-DEFENSE (702-333-3673) for a free consultation. We will investigate every aspect of your case including the FSTs to try to get the charges reduced or dismissed. And if necessary, we can take the matter all the way to trial in pursuit of a not guilty verdict.

We represent clients throughout Nevada, including Las Vegas, Henderson, Washoe County, Reno, Carson City, Laughlin, Mesquite, Bunkerville, Moapa, Elko, Pahrump, Searchlight and Tonopah.

See our article on field sobriety tests in California DUI law.




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