What is the horizontal gaze nystagmus test?
The Horizontal Gaze Nystagmus (HGN) test checks for involuntary jerking of the eyes as they gaze to the side. The test begins by the Deputy placing the tested person in the instructional stance where the feet are placed together and the arms are kept to the side.
How long does it take for nystagmus to appear?
“Distinct nystagmus will be evident when the eye is held at maximum deviation for a minimum of four seconds. People 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.
How do you test for nystagmus?
NHTSA says, “Next, check for onset of nystagmus prior to 45 degrees. Start moving the stimulus toward the right (suspects left eye) at a speed that would take approximately four seconds for the stimulus to reach the edge of the suspects shoulder.
What is the onset angle for vertical nystagmus?
Assuming an onset angle of 30 degrees and the stimulus being held for two seconds to confirm the continuation of nystagmus, each of the four passes in this phase must take at least eight seconds (three seconds out, two second hold, three seconds back) and the four passes together must take at least 32 seconds. xii 9. Vertical Nystagmus.
How long does it take to administer the HGN?
How long does it take for a stimulus to move?
What is the stimulus for the left eye?
Why is the stimulus above eye level?
Is Horizontal Gaze Nystagmus scientific evidence?
Does alcohol cause gaze nystagmus?
Can NHTSA data be used to prove validity?
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How long should HGN test last?
As a practical matter, most HGN administrations should take at least 90 seconds.
How do you test for horizontal nystagmus?
0:002:49Horizontal gaze nystagmus test - HGN - YouTubeYouTubeStart of suggested clipEnd of suggested clipFollow the movement of the stimulus with the eyes only keep looking at the stimulus until told theMoreFollow the movement of the stimulus with the eyes only keep looking at the stimulus until told the test is over do you understand yes now check both eyes for equal pupil size and resting nystagmus.
How does the horizontal gaze nystagmus test work?
The Horizontal Nystagmus Test (HGN) is a standardized field sobriety test (FST) that police often administer in order to gauge whether a DUI suspect is under the influence of alcohol. The officer instructs the suspect to follow (with his eyes) a stimulus to the left and to the right.
How accurate is the horizontal gaze nystagmus test?
The horizontal gaze nystagmus test is only accurate in about 77% of cases. Reasons for a failed test could include: You suffer from a natural nystagmus in your eyes. You have the flu or an inner ear infection.
How do you perform a nystagmus test?
0:121:33How to Check for Nystagmus (With Examples!) - YouTubeYouTubeStart of suggested clipEnd of suggested clipMovement you might see is the eyes shaking from side to side moving faster to one side than to theMoreMovement you might see is the eyes shaking from side to side moving faster to one side than to the other when looking right and left. Similar to the previous.
How do you conduct a HGN test?
To administer the test, the officer will hold a small object approximately 12-15 inches from your nose and slowly move it from one side to the other. You will follow the object with your eyes while keeping your head still. The officer will look for three different clues in each (for a total of six) during the test.
Does HGN work for drugs?
HGN alone had an overall accuracy above chance for all drugs and categories of drugs except marijuana (THC) and any combination of one or more drugs. Note that drugs that are not expected to exhibit HGN, like cocaine, may be found in cases where other drugs causing HGN are present.
What are cops looking for with the pen test?
The HGN test involves the police officer having the driver follow a pen with his eyes. The police officer is looking for specific responses from the eyes that show the driver is under the influence. Nystagmus is the involuntary rapid movement of an eye either horizontally or vertically.
What drugs can cause HGN?
Only 2 things cause Horizontal Gaze Nystagmus: Refer to NHTSA Student Manual VIII-3 The DIP Drugs (Depressants such as alcohol, xanax, valium, etc.; Inhalants, and PCP), and Serious Brain Stem Injury.
What percentage of sober people fail field sobriety test?
5 Reasons You May Fail a Field Sobriety Test While Sober. If you think that the only way to get arrested for a DUI is to drive under the influence, you're mistaken. You don't have to be under the influence to fail a field sobriety test. In fact, about one-third of sober people who take a field sobriety test fail.
How accurate are SFSTs?
SFSTs Accurate at Lower BAC Levels Using the SFSTs, the officers were extremely accurate in discriminating between BACs above and below 0.08 percent. Estimates at the 0.08 level were accurate in 91 percent of the cases, or as high as 94 percent if explanations for some of the false positives are accepted.
Why does alcohol cause HGN?
These hinder the brain's ability to properly control the eye muscles. The presence of such alcohol or drugs in the body's system results in jerking or bouncing movements in the eyeball. The higher a person's blood alcohol content level, the more obvious the nystagmus becomes.
Horizontal Gaze Nystagmus - Is this a reliable DUI test?
1. Field Sobriety Tests & DUI Investigations. Several different kinds of nystagmus exist, only some of them influenced by alcohol. However, the test given at the roadside in a DUI investigation is a test of “horizontal gaze nystagmus.” 2 Horizontal gaze nystagmus refers to an involuntary jerking of the eyes as the eyes gaze toward the side.
HORIZONTAL GAZE NYSTAGMUS: THE SCIENCE AND THE LAW
PREFACE Despite its history of use and the endorsement of the Department of Transportation’s National Highway Traffic Safety Administration, the horizontal gaze nystagmus (HGN)
Fatigue and the Horizontal Gaze Nystagmus Test - Dayton DUI
Charles M. Rowland II has been representing the accused drunk driver for over 20 years. Contact him at (937) 318-1384 if you find yourself facing a DUI (now called OVI) charge.
How long does it take for a nystagmus stimulus to reach the left eye?
Start moving the stimulus toward the right (suspects left eye) at a speed that would take approximately four seconds for the stimulus to reach the edge of the suspects shoulder. Watch the eye carefully for any sign of jerking. When you see it, stop and verify that the jerking continues.
What side of the eye do you check for nystagmus?
NHTSA says, “After you have checked both eyes for lack of smooth pursuit, check the eyes for distinct nystagmus at maximum deviation beginning with the suspects left eye. Simply move the object to the suspects left side until the eye has gone as far to the side as possible.
What is the HGN test?
The Horizontal Gaze Nystagmus (HGN) Field Sobriety Test checks your eyes for involuntary jerking as you gaze to the side. The test begins by the police officer placing the tested person in the instructional stance where the feet are placed together and the arms are kept to the side. The tested person is told to maintain that position until told otherwise and asked if they understand. Once the tested person is in the in the instructional position the Deputy must qualify the tested individual as a candidate for the test by ensuring that the eyes exhibit equal tracking and have equal pupil size. If the eyes do not track equally or the pupils are of different size the person is not a candidate and the test shall not be conducted. (And those symptoms may have other causes than intoxication).
How to check a suspect's left eye?
According to NHTSA, “Check the suspects left eye by moving the stimulus to your right. Move the stimulus smoothly, at a speed that requires approximately two seconds to bring the suspects eye as far to the side as it can go. While moving the stimulus look at the suspect’s eye and determine whether it is able to pursue smoothly. Now move the stimulus all the way to the left, back across suspects face checking if the right eye pursues smoothly. Movement of the stimulus should take approximately two seconds out and two seconds back for each eye. Repeat the procedure”. (P.VIII-7, NHTSA SFST Student Manual, 2002)
What is the HGN field sobriety test?
Horizontal Gaze Nystagmus (HGN) Field Sobriety Test. One of the standardized field sobriety tests (FSTs) used by law enforcement for a DUI arrest is the Horizontal Gaze Nystagmus (HGN) Field Sobriety test, often abbreviated as the HGN FST.
How long does it take for a stimulus to reach the suspect's shoulder?
Now move the stimulus to the left (suspect’s right eye) at a speed that would take approximately four seconds for the stimulus to reach the edge of the suspects shoulder. Watch the eye carefully for any sign of jerking. When you see it stop and verify that the jerking continues.
What is the blood alcohol level for the NHTSA?
The manual used to train all officers in the United States, the NHTSA manual, contains the instructions and strict testing protocol for this test because it is believed to be strongly correlated with alcohol impairment at or above a .08% blood alcohol level. The HGN instructions from the manual read as follows:
HGN Information
Horizontal Gaze Nystagmus (more accurately lateral gaze nystagmus) is a medical term describing the involuntary jerking of the eyes. Officers perform this alleged “scientific” field sobriety test on your eyes.
Why the HGN test is not a good test
First the NHTSA studies concluded the HGN test is only 77% accurate; this assumes that the officers conducted the test correctly. We all have nystagmus, however most of the time it is not detectable by the human eye; alcohol and drugs merely exaggerate this natural nystagmus to make it observable.
How long does it take to administer the HGN?
When the four phases and 14 passes of the HGN are combined, administration of the HGN from the time the stimulus first begins moving must take NOT LESS THAN 82 seconds. Any HGN test that does not contain at least 14 passes and take at least 82 seconds from the time the stimulus first begins moving is improperly administered because it was not administered in accordance with NHTSA protocol and requirements. As a practical matter, most HGN administrations should take at least 90 seconds. Since very few people are 100 percent proficient all of the time, since some pauses during the administration are natural, and since some passes, such as the onset passes may actually take longer than the theoretical minimum, when for instance, the onset is at 40 degrees instead of 30 degrees, any HGN that takes less than 90 seconds is suspect and should be more closely examined for compliance with each individual phase of the test.
How long does it take for a stimulus to move?
The stimulus should be moved at a speed that takes at least two seconds from the center position to the side position. ix At a rate of at least four seconds per eye per pass (two second out to the side and two seconds back to center), this phase of the HGN should take at least 16 seconds.
What is the stimulus for the left eye?
One pass of the stimulus for the left eye, as viewed from the perspective of the person administering it, is the movement of the stimulus from the center position to the right-hand limit of the pass and back to center. One pass of the stimulus for the right eye is the movement of the stimulus from the center position to the left-hand limit ...
Why is the stimulus above eye level?
The stimulus is positioned slightly above eye level in order to cause the person's eyes to open more widely and thus make viewing the eyes easier. vi. 4. Passes -- General. The movement of the stimulus consists of a total of at least 14 passes of the stimulus.
Is Horizontal Gaze Nystagmus scientific evidence?
The majority of States recognize that the Horizontal Gaze Nystagmus (HGN) test is scientific evidence. i As a scientific test it generally requires expert testimony for admissibility. Even States that have found, as a matter of law, that the scientific basis for HGN and the general method of applying it are sufficiently reliable to allow admission ...
Does alcohol cause gaze nystagmus?
While alcohol is a CNS depressant, the HGN is not specific for alcohol. Indeed, alcohol does not even cause nystagmus. Rather, its presence in a person's system simply exaggerates the presence ...
Can NHTSA data be used to prove validity?
Indeed, without such strict compliance, the NHTSA study data cannot be used to evidence validity. iv Importantly, without evidence of validity, the test administration and results are functionally meaningless.
Posted on December 19, 2017 in Uncategorized
- The majority of States recognize that the Horizontal Gaze Nystagmus (HGN) test is scientific evidence.iAs a scientific test it generally requires expert testimony for admissibility. Even States that have found, as a matter of law, that the scientific basis for HGN and the general method of …
The NHTSA Requirements For Administering The HGN Include
- 1. Pretest. The subject should be asked to remove their glasses. The presence of contacts should be noted but contacts need not be removed.v 2. Instructions.The officer should verbally instruct the person to place their feet together and their hands by their side. The officer should verbally instruct the person that they will be asked to follow a stimulus with their eyes and that while the…
Other Common Mistakes
- Other common mistakes in the administration of the HGN include moving the stimulus too quickly -- or less commonly too slowly -- on individual passes, holding the stimulus closer than 12 inches or further away than 15 inches, not holding the stimulus for at least four seconds at maximum deviation, and curving the stimulus upward, downward, or around (also called looping) as it is be…
Manuals
- There are 3 different types or classes of manuals: (1) Student Manuals for the Student Course; (2) Instructor Manuals for the Student Course; and (3) Instructor and Student Manuals for the Instructor Training Course. The links and NTIS Numbers for each follow. Everyone should have, at least, the 1995 and 2000 Student and Instructor Manuals for the basic SFST course. The NHTS…