Horizontal Gaze Nystagumus (HGN) Instructions: (4 out of 6 clues)
1) I am going to check your eyes. Please remove your glasses (if worn)
2) Put your feet together, hands at your side. Keep your head still and follow this stimulus with your eyes only.
3) Keep looking at the stimulus until the test is over.
4) Do not move your head.
5) Do you understand the instructions?
The officer is going to position the stimulus 12-15 inches from the suspect’s nose and slightly above eye level. They are first going to check to see if both pupils of the eye are equal in size (if they aren’t, this may indicate head injury). They are then going to make sure that the eyes are able to track together (called equal tracking) across the suspect’s entire field of vision. This is where the officer makes sees if the eyes track the stimulus together or one eye lags behind the other (this would indicate medical disorder, injury or blindness). After this is done, the officer is going to proceed with the test checking for the below:
Procedures of Horizontal Gaze Nystagmus Testing: The Three Clues (3 in each eye, 6 total)
1) The Lack of Smooth Pursuit – the eyes can be observed to jerk or bounce as they follow a smoothly moving stimulus, such as a pencil or penlight. The eyes of an unimpaired person will follow smoothly, i.e., a marble rolling across a smooth pane of glass, or a windshield wipers moving across a wet windshield. The eyes of an impaired person will follow in a jerking manner, i.e., a marble rolling across sandpaper, or a windshield wiper moving across a dry windshield.
2) Distinct and Sustained Nystagmus at Maximum Deviation – distinct and sustained nystagmus will be evident when the eye is held at maximum deviation for a minimum of four seconds. People will exhibit slight jerking of the eye at maximum deviation, even when unimpaired, but this will not be evident or sustained for more than a few seconds. When impaired by alcohol, the jerking will be larger, more pronounced, sustained for more than four seconds, and easily observable. Nystagmus at maximum deviation is observed when the eye is moved to the point where there is no longer any white left in the side of the eye and when nystagmus is observed the eye will act in a back and forth “popping" motion.
3) Onset of Nystagmus Prior to 45 Degrees – the point at which the eye is first seen jerking. If the jerking begins prior to 45 degrees (which is typically when the stimulus is approximately out to the D’s shoulder) it is evident that the person has a B.A.C. (breath alcohol content) above 0.08, as shown by recent research.
The higher the degree of impairment, the sooner the nystagmus will be observable.
Walk and Turn (WAT) Instructions: (2 out of 8 clues)
1) Put your left foot on the line, then your right foot on the line ahead of your left. Keep your arms at your side (Demonstrate)
2) Do not start until I tell you to do so.
3) Do you understand? (Officer must receive an affirmative response)
4) When I tell you to begin, take 9 heel-to-toe steps on the line. (Demonstrate) To turn around, keep one foot on the line and return nine steps.
5) When you turn on the ninth step, keep your front foot on the line and turn taking several small steps with the other foot. (Demonstrate) Take 9 heel-to-toe steps back down the line.
6) Keep your arms at your side at all times, watch your feet, and count each step out loud. Once walking begins, do not stop until you’ve completed the test.
7) Do you understand the instructions?
8) You may begin.
*** If suspect doesn’t understand some part of the instructions, officer should repeat only that part which suspect does not understand.
The Walk and Turn Exercise is divided into two phases: 1) Instructions Stage and 2) Walking Stage.
During the Instructions Stage, the subject must stand with their feet in heel-to-toe position, keep their arms at their sides, and listen to the instructions.
During the Walking State, the subject must perform and complete the exercise as instructed.
There are 8 clues that an officer is looking for during the WAT exercise, 2 during the Instructions Stage and 6 during the Walking Stage. They are as follows:
Instructions Stage clues:
1) Can’t balance during instructions
2) Starts too soon
Walking Stage clues:
1) Stops while walking
2) Doesn’t touch heel-to-toe
3) Steps off line
4) Uses arms for balance (raises more than 6 inches)
5) Loses balance on turn or turns incorrectly
6) Takes the wrong number of steps
WAT Testing Conditions – WAT requires a designated straight line (although a line is NOT required to administer the exercise), and should be conducted on a reasonably dry, hard, level, and non-slippery surface. There should be sufficient room for suspects to complete nine heel-to-toe steps. **Note: Recent field validation studies have indicated that varying environmental conditions have not affected a suspect’s ability to perform this exercise.
The original research indicated that certain individuals over 65 years of age, back, leg or middle ear problems had difficulty performing this exercise. **This does not mean that it is an excuse that is available to every Defendant in this category, just ONE factor that needs to be considered when evaluating the case.
One-Leg-Stand (OLS) Instructions: (2 out of 4 clues)
1) Stand with your feet together and your arms at your side. (Demonstrate)
2) Maintain position until told otherwise.
3) Do you understand? (Officer must receive an affirmative response)
4) When I tell you to, I want you to raise one leg (either leg) approximately six inches off the ground, foot pointed out, both legs straight, and look at the elevated foot.
5) Count out loud in the following manner: 1001, 1002, 1003, and so on, until told to stop. (Demonstrate raised leg and count)
6) Do you understand the instructions?
7) You may begin the test.
The timing for a thirty-second period by the officer is an important part of the OLS test. The original research has shown that many impaired subjects are able to stand on one leg for up to 25 seconds, but that few can do so for 30 seconds.
The One-Leg-Stand is divided into two phases: 1) Instructions Stage and 2) Balance and Counting Stage.
During the Instructions Stage, the subject must stand with their feet together, keep their arms at their sides, and listen to the instructions.
During the Balance and Counting State, the subject must perform and complete the exercise as instructed.
There are 4 clues that an officer is looking for during the OLS exercise. They are as follows:
1) Sways while balancing
2) Uses arms for balance (raises more than 6 inches)
4) Puts foot down
OLS Testing Conditions – OLS requires a reasonably dry, hard, level, and non-slippery surface. The original research indicated that certain individuals over 65 years of age, back, leg or middle ear problems, or people who are overweight by 50 or more pounds had difficulty performing this exercise. **This does not mean that it is an excuse that is available to every Defendant in this category, just ONE factor that needs to be considered when evaluating the case.