Standardized Field Sobriety Tests for DUI Cases
The National Highway Traffic Safety Administration (NHTSA) recognizes three standardized field sobriety tests designed to identify intoxication responses from drivers. The officer should instruct the driver on performing a field sobriety test.
The three tests include the following:
- Horizontal Gaze Nystagmus Test (HGN Test)
- Walk-and-turn test (WAT)
- One-leg-stand test (OLS)
Horizontal Gaze Nystagmus Test
During this test, an officer holds a small object about twelve inches from the driver’s face, such as a pen or flashlight.
They then move the object across the driver’s line of sight. The officer instructs the driver to focus on the moving object while standing. If the driver’s eyes jerk more than usual, they are deemed to have a higher-than-average blood alcohol concentration level.
In the walk-and-turn test, the police need the subject to take heel-to-toe steps in a straight line while counting out loud. They then turn around and take the same steps back.
The importance of the test is to identify the driver’s ability to divide attention. Besides maintaining balance, the drivers should be able to follow instructions on the number of steps to be taken, when to turn, and counting out loud.
The officers use the test to grade the driver on certain clues, including:
- Lack of balance
- Starting pace
- Stopping while walking
- Failure to touch heel to toe
- Stepping off the line
- Balancing with arms
- Making improper turns
- Counting the number of steps incorrectly
The One-Leg-Stand Test
During the one-leg stand tests, the officer instructs the driver to stand on one leg, raising the other approximately six inches off the ground. The driver then may be instructed to count to a specific number simultaneously.
Law enforcement officers use this test to look for the following clues to determine intoxication:
- Balancing with arms
- Putting the leg down
Show Probable Cause
In DUI investigations, police rank FST performance higher than some other factors. Suppose a defendant argues about an unlawful arrest due to insufficient evidence or probable cause. The arresting officer can testify using the defendant’s FST result.
In that case, the arrest will be lawful due to probable cause. If the facts support the claim, the defendant’s arrest becomes lawful. Some of the factors that determine probable cause include:
- The smell of alcohol inside the car
- The driving pattern
- Manner of speech
- Driver’s appearance
Eligibility of FST Performance
In some cases, an officer’s FST observation can be ineligible evidence in court. Therefore, the judge might require a professional’s testimony on the relevance of the FST results. They may need to know how the FST impairment proof gives evidence of intoxication.