Standardized Field Sobriety Tests

What are SFSTs?

Police might conduct several tests at the side of the road to evaluate possible impairment. These might include an alphabet test, counting backwards, finger counting, lack of convergence test, modified Romberg test, horizontal gaze nystagmus, walk-and-turn and one-leg-stand test. Only the last three of these are standardized tests, meaning there is some research to support a finding that a person may be over the legal limit if they display sufficient clues on the tests.


Research suggests that, if the tests are done appropriately, there is an 88% probability that a person is over the legal limit for alcohol if they display 4 out of a 6 possible clues on the horizontal gaze nystagmus test, 79% probability if they display 2 out of a possible 8 clues on the walk-and-turn test, and 83% probability if they display 2 out of 4 possible clues on the one-leg-stand test. Officers must perform the tests correctly for these results to be admissible in court. However, in Ohio they need not perform the tests perfectly, but rather must "substantially comply" with the instructions for performing the tests as found in the current 2023 NHTSA SFST Manual (here is the 2018 NHTSA manual)

Horizontal Gaze Nystagmus (HGN)

The HGN test involves the officer moving his finger or pen side to side as the person follows the stimulus with their eyes only. This test is not evaluating the person's ability to keep their eyes on the pen. Rather, it is performed to detect horizontal nystagmus, which in plain English means a slight shaking of the eyes side to side. The officer should start by ensuring there are no flashing lights or other conditions that may affect the results while asking questions about potential medical conditions that might affect the test. The officer will then move on to an instruction phase.

Instruction Phase:

The Officer should begin the test with the following instructions:

• Put your feet together, hands at your side.
  
• Keep your head still.
• I am going to check your eyes.
• Keep your head still and follow this stimulus with your eyes only.
• Keep focusing on the stimulus until I tell you to stop, do you understand?
• Proceed after receiving an affirmative response from the suspect.

The Officer should also have the person remove any glasses before beginning the test.

Medical Evaluation Phase:

There are many things that can cause HGN other than alcohol use. In addition to asking questions about such other conditions, the officer must start the HGN by performing two screening techniques.

HGN Test 1 - Lack of Smooth Pursuit:

The testing phase of the HGN begins with checking for a lack of smooth pursuit. The officer should perform the test as follows:

• Position the stimulus approximately 12-15 inches from the suspect’s nose and slightly above eye level.
  
• Move the stimulus smoothly from the center position out to the right where the eye can go no further, then back across the subject’s face all the way out to the left side where the eye can go no further and then back to the center.  
• Movement of the stimulus should take approximately two seconds out and two seconds back to the center for each eye.
• A total of two (2) passes should be made.

HGN Test 2 - Distinct and Sustained Nystagmus at Maximum Deviation:

The second testing phase of the HGN is to check for distinct and sustained nystagmus when the stimulus reaches maximum deviation. The officer should perform the test as follows:

• Position the stimulus approximately 12-15 inches from the suspect’s nose and slightly above eye level.
  
• Move the stimulus to the right side where the eye can go no further.  
• Hold the stimulus steady at this position for a minimum of four (4) seconds, and observe the eye for distinct and sustained nystagmus.  
• Move the stimulus back across the suspect’s face all the way out to the left side.
• Hold the stimulus steady at this position for a minimum of four (4) seconds, and observe the eye for distinct and sustained nystagmus.  
• A total of two (2) passes should be made.

HGN Test 3 - Onset of Nystagmus Prior to 45 Degrees:

The third testing phase of the HGN is to check for onset of nystagmus prior to 45 degrees (i.e., if the eyes start to shake before the stimulus reaches a 45 degree angle from the center of the person's face). The officer should perform the test as follows:

• Position the stimulus approximately 12-15 inches from the suspect’s nose and slightly above eye level.
  
• Move the stimulus slowly towards the right at a speed that would take about four (4)seconds for the stimulus to go just beyond the edge of the suspect’s left shoulder.
• Once the clue is observed, pause momentarily and note that it occurred prior to 45 degrees, and then return the stimulus to the center of the suspect’s face.
• From this position move the stimulus to the left at a speed that would take about four (4) seconds for the stimulus to go just beyond the edge of the suspect’s right shoulder.  
• Once the clue is observed, pause momentarily and note that it occurred prior to 45 degrees, and then return the stimulus to the center of the suspect’s face.
• A total of two (2) passes should be made.

Vertical Nystagmus:

Many officers will then continue to check for nystagmus while moving the stimulus up and down; however, this is NOT part of the standardized tests.

Clues: (4 out of a possible 6 clues indicate a BAC over .08)

There are 6 possible clues on the HGN, 1 for each eye on each of the three tests (lack of smooth pursuit, distinct and sustained nystagmus at maximum deviation, and onset of nystagmus prior to 45 degrees).

Walk-and-Turn

The walk-and-turn test does not merely test whether a person can walk a straight line, but rather it tests the person's ability to divide their attention and clues are marked if the person does not walk the line just as instructed. The tests begins with an instruction phase before moving on to the walking and balancing phase.

Instruction Phase:

• Give the following commands from a safe position.
  
• "Place your left foot on the line.”
• “Place your right foot on the line ahead of the left foot, with heel of right foot against the toe of the left foot and place your arms down at your side.”
• Give a demonstration of this procedure simultaneously.
• “Keep this position until I tell you to begin.”
• “Do not start to walk until I tell you to do so.”
• “Do you understand the instructions so far?”
• Receive an affirmative response before continuing

Walking and Counting Phase:

• Give the following commands from a safe position.
  
• “Take nine heel-to-toe steps down the line, turnaround, and take nine heel-to-toe steps back up the line.”  
• Demonstrate three heel-to-toe steps, emphasizing “heel to toe”
• “Keep the front foot on the line, and turn by taking a series of small steps with the other foot.”
• Demonstrate the turn.
• “Watch your feet at all times.”
• “Count the steps out loud.”
• “Keep your arms at your side at all times.”
• “Once you start walking, do not stop until you have completed the test.”
• “Do you understand the instructions so far?”  
• Receive an affirmative response before continuing.
• “Count your first step from the heel-to-toe position as number one.”

Clues: (2 out of 8 clues indicates BAC over .08)

One-Leg-Stand

For the one-leg-stand test, the person must stand on one leg for at least thirty seconds while the officer times the test.

Instruction Phase:

• Give the following commands from a safe position.
  
• “Stand with your feet together and arms at your side.”
• Demonstrate for a few seconds.
• “Do not start the test until I tell you to do so.”
• “Do you understand the instructions so far?”
• Receive an affirmative response before continuing.

Counting and Balancing Phase:

• Give the following commands from a safe position.
  
• “Raise one leg (either leg) approximately six(6) inches off the ground, with your raised foot parallel to the ground.”
• Demonstrate this position.
• “Keep both legs straight, arms by your sides, and look at the elevated foot.” 
• “Count out loud in the following manner: 1001, 1002, 1003 and so on until told to stop.” 
• “Do you understand the instructions so far?”
• Receive an affirmative response before continuing.
• “Go ahead and begin the test.”
• Officer should time the 30 seconds. Test should be stopped 30 seconds is up.

Clues: (2 out of a possible 4 clues indicates a BAC over .08).

• Swaying
  
• Uses arms for balance.
• Hopping
• Putting foot down before 30 seconds elapse.

Conclusion

This is just a brief overview of SFSTs. As a general rule, it is best to decline a request to take these tests.

An experienced OVI attorney will evaluate how the tests were performed, the instructions, the demonstrations, the conditions, the performance on the tests and the various research studies regarding the tests. At Smith's Law Offices, our attorneys have completed the same NHTSA Standardized Field Sobriety Testing and Advanced Roadside Impaired Driving Enforcement (ARIDE) course that the police receive. We know how to evaluate and take the tests apart because, in addition to our legal research, we have been certified as being able to perform the tests ourselves.