The "Voo Doo" Eye test:

Does the HGN test indicate that a person is intoxicated ?  Not necessarily.  The Court of Special Appeals in Maryland in Schultz v. State, 664 A.2d 60, 77 (Md. App. 1995) gave judicial notice to 38 causes of HGN unrelated to alcohol including:

 (1) problems with the inner ear labyrinth; (2) irrigating 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 hemorrhage; (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) some prescription drugs, tranquilizers, pain medications, anti-convulsants; (28) barbiturates; (29) disorders of the vestibular apparatus and brain stem; (30) cerebellum dysfunction; (31) heredity; (32) diet; (33) toxins; (34) exposure to solvents, PCBs, dry-cleaning fumes, carbon monoxide; (35) extreme chilling; (36) lesions; (37) continuous movement of the visual field past the eyes; and, (38) antihistamine use.  

The problem is not just in identifying the cause of HGN but also in being able to identify HGN from other forms of nystagmus.

 There are also forty seven types of nystagmus in individuals, separate from Horizontal Nystagmus: (1) Acquired; (2) Anticipatory (induced); (3) Arthrokinetic (induced, somatosensory); (4) Associated (induced, Stransky’s); (5) Audio kinetic (induced); (6) Bartel’s (induced); (7) Brun’s; (8) Centripetal; (9) Cervical (neck torsion, vestibular-basilar artery insufficiency); (10) Circular/Elliptic/Oblique (alternating windmill, circumduction, diagonal, elliptic, gyratory, oblique, radiary); (11) Congenital (fixation, hereditary); (12) Convergence; (13) Convergence-evoked; (14) Dissociated (disjunctive); (15) Downbeat; (16) Drug-induced (barbituate, bow tie, induced); (17) Epileptic (ictal); (18) Flash induced; (19) Gaze-evoked (deviational, gaze-paretic, neurasthenic, seducible, setting-in); (20) Horizontal; (21) Induced (provoked); (22) Intermittent Vertical; (23) Jerk; (24) Latent/Manifest Latent (monocular fixation, unimacular); (25) Lateral Medullary; (26) Lid; (27) Miner’s (occupational); (28) Muscle-Paretic (myasthenic); (29) Optokinetic (induced, optomotor, panoramic, railway, sigma); (30) Optokinetic After-Induced (post-optokinetic, reverse post-optokinetic); (31) Pendular (talantropia); (32) Periodic/Aperiodic Alternating; (33) Physiologic (end-point, fatigue); (34) Pursuit After-induced; (35) Pursuit Defect; (36) Pseudo spontaneous; (37) Rebound; (38) Reflex (Baer’s); (39) See-Saw; (40) Somatosensory; (41) Spontaneous; (42) Stepping Around; (43) Torsional; (44) Uniocular; (45) Upbeat; (46) Vertical; (47) Vestibular (ageotropic, geotropic, Bechterew’s, caloric, compensatory, electrical/faradic/galvanic, labyrinthine, pneumatic/compression, positional/alcohol, pseudo caloric

Click here to read Mimi's SFST paper