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The Technology of Field Sobriety Tests

Posted by Aaron J. Wolff | Aug 15, 2012 | 0 Comments

If you are stopped by a police officer during a traffic stop, you may be requested to perform standardized field sobriety tests (FSTs) if the officer suspects that you may be driving under the influence (DUI). If you are found guilty of DUI, then you will want to contact a qualified DUI attorney.

According to the National Highway Transportation and Safety Administration (NHTSA), there are three different tests that are proven to scientifically establish whether or not a suspect is under the influence and whether or not there is probable cause for arrest. The three tests that are used are as follows:

  • Horizontal Gaze Nystagmus (HGN)
  • Walk-and-Turn (WAT)
  • One-Leg Stand (OLS)

If you are asked to perform FSTs when an officer pulls you over, you have the right to refuse. Field sobriety tests are not required under Washington state law. However, this does not get you off the hook, and your refusal may be used by the prosecutor in court to argue “consciousness of guilt.” If an officer asks you for a breathalyzer test, you may also refuse, but anticipate the officer placing you under arrest for suspicion of DUI. Once arrested, you will be taken to the police station (or hospital) and asked to submit to a breath (or blood) test. You have the right to refuse this test as well, but a refusal of this test means far greater consequences.

Law enforcement must administer the field tests according to their training and protocol. NHTSA has standardized these tests so that they must be administeredi in an exact manner or else the validity of the results iscompromised.

For the first FST, the Horizontal Gaze Nystagmus (HGN), the officer will ask you to follow an object or his finger with your eyes and then judge your response. The officer will look for signs of nystagmus (eyeball jerking) as your pupils follow the movement of the object.

The second test is the Walk-and-Turn (WAT), and you will be asked to take nine heel-to-toe steps in a straight line. For this test to be administered correctly, the officer must provide you with a line. Yet many officers ignore this and ask the suspect to walk an imaginary line instead. As you walk the line, officers will look for the following:

• Lack of balance during instruction phase
• Starting the walk too early
• Stepping “off” the line
• Failing to touch heel to toe on any step
• Stopping at any point during the test
• Using your arms for balance
• Raising your arms more than six inches from your sides
• Making an improper number of steps
• Turning improperly

Once you have taken the nine steps, you will be asked to turn a specific way and walk back on the same path you took. If you demonstrate two or more of the above on ether of the 9 steps forward or back, you are considered to have failed that test.

For the One-Leg Stand (OLS) FST, you will be asked to count with one leg off the ground until told to stop. There are four clues that the officer will look for:

• Swaying while balancing

• Raising your arms

• Putting your foot down

• Hopping

Because FSTs are considered to be scientific in nature, they are taken under advisement differently in court. For this reason, a common DUI defense is to challenge whether or not the tests were administered with complete compliance to established protocols.

Seattle DUI attorneys at Wolff Defense are familiar with the ins and outs of proving whether or not the FSTs and other sobriety tests have been given according to DUI Washington State laws. If you have been charged with DUI, give us a call today to discuss your case. Don’t fight your DUI charge alone.

About the Author

Aaron J. Wolff

A former DUI prosecutor, Aaron Wolff has over 18 years of experience in representing people accused of DUI and is recognized as one of the leading defense lawyers in Washington State. His relentless and passionate advocacy has lead to superb ratings and outstanding reviews from former clients.


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