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Understanding DUI Field Sobriety Tests in Idaho


Idaho is one state in the U.S. that takes the offense of driving under the influence (DUI) seriously. A single DUI charge can have far-reaching effects on you, even if it’s your first. When the police stop you, they often conduct some tests on the scene to know if you’re intoxicated. These tests are called Field Sobriety Tests.

Depending on your performance in the FSTs, the police officer may then have probable cause for blood and breath analysis. If the police arrest you for a DUI and have you perform FSTs, you need a Boise DUI lawyer.

If you don’t understand how these tests work, you may perform poorly and increase your chances of being convicted. That is why we have written this article.

3 Major Field Sobriety Tests Used in Idaho

There are many Field Sobriety Tests an Idaho police officer can administer to check your sobriety. Below we discuss three significant tests. We chose these three because the National Highway Traffic and Safety Administration (NHTSA) endorsed them as standard tests.

  • Horizontal Gaze Nystagmus (HGN)

Nystagmus refers to the rapid involuntary movement of the eyes from side to side. Alcohol exaggerates this jerking, so check for that exaggeration as a test of impairment. HGN does not affect your vision, so even if you’re intoxicated, you won’t notice the jerks.

A police officer administering this test will either do so in a bright place or with a flashlight. The officer then asks the subject to follow an object with their eyes. The item could be a pen or a finger. There are three signs the police will look for to prove your intoxication. They are:

  • Inability to follow the object smoothly.
  • Distinct nystagmus at maximum deviation (where the eye has moved to one side).
  • Whether your nystagmus is within 45 degrees of center.
  • Walk-and-Turn Test 

This Field Sobriety Test requires that you walk heel-to-toe on an imaginary line and take some steps backward too. The police officer administering the test will ask that you keep your arms at your side, watch your feet and count your steps loudly. The officer will first give you these instructions before asking you to perform them.

As you walk, the officer will also watch out for signs of intoxication, which include:

  • Difficulty in maintaining balance
  • Walking before the officer completes the instruction phase
  • Inability to walk heel-to-toe
  • Stepping out of line
  • Incorrect turns or wrong number of steps
  • One-Leg Stand

The one-leg stand test is a divided attention test. The police officer who stopped you will ask you to raise one of your legs about six feet above the ground. You’re to keep your arms by your side and count in thousands (one-thousand-one, one-thousand-two, etc.). The officer will also instruct that your eyes always remain on your raised feet.

While in this position, the police officer will look out for these indicators of intoxication:

  • Swaying
  • Balancing with your arms
  • Dropping your foot or hopping
  • Difficulty in counting

This test only has a 65% accuracy, so your DUI lawyer in Boise can easily challenge it. The police shouldn’t subject some persons to this test. This restricted class includes elderly, overweight, and infirm persons.

You Can Challenge a Field Sobriety Test

Although these are widely used and standardized tests, they aren’t perfect. The tests are not infallible means of proving intoxication. Many factors can make a driver perform poorly on a Field Sobriety Test. Some of them include:

  • Old age
  • Injury
  • Sickness
  • Poor eyesight and darkness
  • Bad weather conditions
  • Bad footwear
  • Uneven roads

A police officer may wrongly conclude that a driver is driving under the influence because of these factors. A perfectly sober driver may not even pass these tests. If the police make you take these tests and think you failed because of any of these factors, you should tell your DUI attorney. A good lawyer can successfully challenge any evidence the police obtained through flawed testing.

Boise DUI Lawyers Can Get You Off on a DUI Charge

If the police arrest you on a DUI charge, you’re looking at stiff penalties if the court convicts you. The local district attorney will find it easier to get a conviction if you failed a field test. However, at trial, an excellent Boise DUI attorney can get you off or reduce your punishment.

Fighting a DUI charge without a lawyer is a dangerous move. The Idaho legal system is such that only a skilled DUI lawyer can successfully defend you. At Boise DUI, we have represented many clients, and we can win your case for you. So, if the police ever arrest you for a DUI, call us immediately.