Walking the Line: Standardized Field Sobriety Tests in Texas
The National Highway Traffic Safety Administration (NHTSA) developed a series of three tests to assist law enforcement in confirming whether a stopped driver is driving under the influence of drugs or alcohol. The series includes the Walk-And-Turn (WAT), the One-Legged Stand (OLS) and the Horizontal Gaze Nystagmus (HGN) test.

July 17, 2011 /24-7PressRelease/ -- The National Highway Traffic Safety Administration (NHTSA) developed a series of three tests to assist law enforcement in confirming whether a stopped driver is driving under the influence of drugs or alcohol. The series includes the Walk-And-Turn (WAT), the One-Legged Stand (OLS) and the Horizontal Gaze Nystagmus (HGN) test.

Walk and Turn (WAT)

When performing the WAT field sobriety test, you will be required to walk in a straight line, heel-to-toe. After 9 steps, you must turn on one foot and walk back in the same manner. The police officer will be watching for a total of 8 indicators while the WAT is being described and administered, including whether you:
- Kept your balance during explanation of the test
- Waited until the instructions were finished to begin the test
- Stopped while walking to regain your balance
- Touched the heel of one foot to the toe of the other while walking the line
- Stepped off the line while walking
- Used your arms for balance while walking
- Turned improperly
- Took more or less than 9 steps

Research indicates that 79 percent of those who fail two of the indicators have a blood alcohol concentration of 0.08 or higher.

One-Legged Stand (OLS)

The OLS is exactly what it's named: you must stand on one foot, counting out loud (one-one thousand, two-one thousand, etc.) until the police officer instructs you to stop. The test usually lasts for 30 seconds. The police officer will again be looking for indicators related to balance including swaying, using your arms for balance, hopping to keep falling and putting your foot down before you're told to do so.

Eighty-three percent of those who have two or more issues with balance have a blood alcohol concentration of 0.08 or higher.

Horizontal Gaze Nystagmus (HGN)

The HGN test requires you to follow a slowly-moving object, typically a pen or a flashlight, with your eyes only. Nystagmus is an involuntary jerking motion that happens naturally as you gaze sideways. However, in impaired drivers, nystagmus may occur sooner than in those who are not impaired. The police officer will be watching to see if you are able to smoothly follow the object, if your eye jerks when you've looked as far right or left as possible and how far from center you were looking when your eye began to jerk.

After testing both eyes, 88 percent of those who exhibit 4 or more indicators usually have a blood alcohol concentration of 0.08.

Field Sobriety Tests Are Far From Perfect

As noted above, none of those making up the Standardized Field Sobriety Tests (SFTS) series are 100 percent perfect, meaning that you may fail the test despite not having a blood alcohol concentration above the legal limit. The NHTSA specifically notes that those who take anti-seizure medication and some other drugs may also fail the HGN test.

There are other factors that may affect your ability to successfully pass the SFTS including the simple fact that you're being asked to complete non-standard activities at 2 am, under the watchful eye of local police who are waiting for you to fail. Even a breath test can lead to inaccurate results.

If an officer asks you to step out of the car and perform a field sobriety test, you do have the right to politely decline. You will most likely be arrested and taken into custody if you do, but at the same time you may be limiting the evidence that the police have against you as well.

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