Horizontal Gaze Nystagmus (HGN)

Officers who suspect a driver of DUI often conduct field sobriety tests to gather evidence to support the alleged violation. One (1) of three (3) standardized field sobriety tests recognized by the National Highway Transportation Safety Administration (NHTSA) is the horizontal gaze nystagmus test. A DUI defense lawyer experienced in defending drunk driving cases can effectively challenge the outcome of the horizontal gaze nystagmus (HGN) test and other field sobriety tests. Attorney Brandon Daniels is a former police officer and has been trained in the Standard Field Sobriety Tests. This training along with his experience as a DUI defense attorney and member of the National College for DUI Defense, provide him unique qualifications to defend his clients charged with DUI.

What is Horizontal Gaze Nystagmus (HGN)?

The American Academy of Opthamology defines it as ” involuntary, rapid and repetitive movement of the eyes. Usually the movement is side-to-side (horizontal nystagmus), but it can also be up and down (vertical nystagmus) or circular (rotary nystagmus). The movement can vary between slow and fast, and it usually involves both eyes.”. Officers want you to believe that alcohol is the only reason that you would have nystagmus, but that certainly is not the case. Nystagmus, or involuntary jerking of the eye, occurs in everyone naturally, regardless of whether he or she has been drinking. Alcohol and drugs magnify the nystagmus effect, but so can a variety of other factors, including illness or injury.

There are thirty-eight causes of HGN, alcohol is just one. The complete list is as follows:
  1. problems with the inner ear labyrinth
  2. irrigation of the ears with warm or cold water under peculiar weather conditions
  3. influenza
  4. streptococcus infection
  5. vertigo
  6. measles
  7. syphilis
  8. arteriosclerosis
  9. muscular dystrophy
  10. multiple sclerosis
  11. korchaff’s syndrome
  12. brain hemorage
  13. epilepsy
  14. hypertension
  15. motion sickness
  16. sunstroke
  17. eyestrain
  18. eye muscle fatigue
  19. glaucoma
  20. changes in atmospheric pressure
  21. consumption of excessive amounts of caffeine
  22. excessive exposure to nicotine
  23. aspirin
  24. circadian rhythms
  25. acute trauma to the head
  26. chronic trauma to the head
  27. prescription drugs, tranquilizers, pain medications & anti-convulsants
  28. barbituates
  29. disorders of the vestibular apparatus and brain stem
  30. cerebellum dysfunction
  31. heredity
  32. diet
  33. toxins
  34. exposure to solvents, PCB’s, dry-cleaning fumes, carbon monoxide
  35. extreme chilling
  36. lesions
  37. continuous movement of the visual field past teh eyes
  38. antihistamine use

The higher the blood alcohol concentration, the sooner the eyes will begin jerking as they move from side to side. In addition to eye movement, nystagmus symptoms include sensitivity to light, dizziness, difficulty seeing in darkness, vision problems, holding the head in a turned or tilted position or feeling that the world is shaking. The American Association of Opthamology indicates that you can witness nystagmus for yourself by performing the following test: “spin an individual around for about 30 seconds, stopping, and then having them try to stare at an object. If nystagmus is present, the eyes will first move slowly in one direction, then move rapidly in the opposite direction”.

Officers are taught to administers the test by asking the driver to follow a small stimulus, such as the tip of a pen, with their eyes, while keeping their head still. The officer should be evaluating an individual based on three (3) different criteria. They look for a lack of smooth pursuit as the eyes move, sustained jerking when the eye reaches the furthest point and lastly, they look for the onset of jerking prior to the eye reaching a 45-degree angle.

Each of these three factors, clues or indicia are counted in each eye. If the officer observes a total of four (4) out of the six (6) possible clues, NHTSA says that the officer may assume that there is a 77 % chance that the driver’s blood alcohol content (BAC) is above Florida’s legal limit of .08 %, and the driver may be arrested for Driving Under the Influence (DUI). The 77% finding requires that the officer administered the test properly and fully understands what they are observing. This allows for a 23% chance that the individual was not under the influence of alcohol according to NHTSA. No individual that we know wants to wager their freedom on the officers understanding of complex medical conditions and trust an officer that they are impaired when there is a 23% chance that the officer is wrong.

As you can now see, the horizontal gaze nystagmus (HGN) test is far from foolproof and should not be used for the basis of an arrest for DUI alone. Experts conclude that when it comes to alcohol intoxication, mental impairment always comes before physical impairment. Therefore, the mere presence of a type of physical impairment, such as horizontal gaze nystagmus caused by illness or injury, would not support a charge of drunk driving and your experienced DUI defense lawyer will be able to show this in court. These are all reasons why you should fight your DUI. To read more on HGN, visit the DANIELS & HANNAN Blog.

Daniels & Hannan, your Southwest Florida DUI defense firm knows that the DUI is a very serious charge. That is why we fight hard for our clients' rights and freedom. We utilize experts in the area of ophthalmology at trial to refute the rudimentary training of the officer and show juries all the other possibilities that actually could have existed when the officer mistakenly believed alcohol was the contributing factor in the HGN test administered.

If you have been charged with DUI, Section 316.193, Florida Statutes, you have rights. Contact the aggressive DUI lawyers, Daniels & Hannan, today at (941) 932-8007 or simply complete our confidential contact form for a free case evaluation.

At Daniels & Hannan our Attorneys are able to handle any DUI or drinking-related traffic violation that you have and we offer you the personal attention you deserve. Our office staff and Attorneys are able to walk you the best options for defending your rights and explain how it will work from beginning to end.

If you have a DUI or any traffic violation and are in need of a reputable lawyer to represent you, please contact DANIELS & HANNAN to schedule your free consultation at (941) 932-8007 or email This email address is being protected from spambots. You need JavaScript enabled to view it.

DANIELS & HANNAN Attorneys at Law provide experienced legal services in Criminal Defense, Family Law, Divorce Law, DUI Defense, Personal Injury, and Business Law. Providing full service legal representation throughout Southwest Florida with primary offices located in Lakewood Ranch Florida representing clients’ in Sarasota, Manatee, Pinellas, Hillsborough, Polk, and Charlotte counties. DANIELS & HANNAN has the experience needed to manage legal matters before Florida State, County, and Federal Courts in Clearwater, Bradenton, Sarasota, St. Petersburg, Tampa, Venice, Fort Meyers, Naples, and others throughout Southwest Florida.