September 2006

In Chapter 8 of NHTSA’s “DWI Detection and Standardized Field Sobriety Testing” Manual is a subsection entitled “Overview of Nystagmus”:

Nystagmus is defined as an involuntary jerking of the eyes. Alcohol and certain other drugs cause Horizontal Gaze Nystagmus.

Categories of Nystagmus

There are three general categories of nystagmus:

1. Vestibular Nystagmus is caused by movement or action to the vestibular system.

2. Nystagmus can also result directly from neural activity.

3. Nystagmus may also be caused by certain pathological disorders

Vestibular Nystagmus is caused by movement or action to the vestibular system.

A. Types of vestibular nystagmus:

Rotational Nystagmus occurs when the person is spun around or rotated rapidly, causing the inner fluid in the ear to be disturbed. If it were possible to observe the eyes of a rotating person, they would be seen to jerk noticeably.

Post Rotational Nystagmus is closely related to rotational nystagmus: when the person stops spinning, the fluid in the inner ear remains disturbed for a period of time, and the eyes continue to jerk.

Caloric Nystagmus occurs when fluid motion in the canals of the vestibular system is stimulated by temperature as by putting warm water in one ear and cold in the other.

Positional Alcohol Nystagmus (PAN) occurs when a foreign fluid, such as alcohol, that alters the specific gravity of the blood is in unequal concentrations in the blood and the vestibular system.

Nystagmus can result directly from neural activity:

Optokinetic Nystagmus occurs when the eyes fixate on an object that suddenly moves out of sight, or when the eyes watch sharply contrasting moving images. 

Examples of optokinetic nystagmus include watching strobe lights, or rapidly moving traffic in close proximity. The Horizontal Gaze Nystagmus test will not be influenced by optokinetic nystagmus when administered properly.

Physiological Nystagmus is a natural nystagmus that keeps the sensory cells of the eyes from tiring. It is the most common type of nystagmus. It happens all the time, to all of us. This type of nystagmus produces extremely minor tremors or jerks of the eyes. These tremors are generally too small to be seen with the naked eye. Physiological nystagmus will have no impact on our (NHTSA) Standardized Field Sobriety Tests, because its tremors are generally invisible.

Gaze Nystagmus occurs as the eyes move from the center position. Gaze nystagmus is separated into three types:

(1) Horizontal Gaze Nystagmus occurs as the eyes move to the side. It is the observation of the eyes for Horizontal Gaze Nystagmus that provides the forst and most accurate test in the Standardized Field Sobriety Test battery. Although this type of nystagmus is most accurate for determining alcohol impairment, its presence may also indicate the use of other drugs.

(2) Vertical Gaze Nystagmus (VGN) is an involuntary jerking of the eyes (up and down) which occurs when the eyes gaze upward at maximum elevation. The presence of this type of nystagmus is associated with high doses of alcohol for that individual and certain other drugs. The drugs that cause Vertical Gaze Nystagmus are the same ones that cause horizontal Gaze Nystagmus.

Note: There is no drug that will cause Vertical Gaze Nystagmus that does not cause Horizontal Gaze Nystagmus. If Vertical Gaze Nystagmus is present and horizontal Gaze Nystagmus is not, it could be a medical condition.

(3) Resting Nystagmus is referred to as a jerking of the eyes as they look straight ahead. Its presence usually indicates a pathology or high doses of a Dissociative Anesthetic drug such as PCP. If detected, take precautions.  (Officer Safety)

My practice focuses exclusively on criminal defense, with the majority of my cases involving DWI and DUI representation.  The only exception to the "only criminal defense" rule is that I handle proceedings such as Administrative License Revocation hearings which arise out of DWI charges (technically civil, but from a practical standpoint, they are criminal in nature).

I practice in Austin, Texas, all across Travis County, and, in the surrounding counties of Williamson, Hays and Bastrop.

Please feel free to email me if you have questions about DWI. 

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Jamie Spencer, Attorney. at Law

Phone:  (512) 472 9909
Fax:       (512) 472 9908

Office and Mailing Address
812 San Antonio Street Suite 403
Austin, Texas 78701


My entire legal career has been devoted to helping people who have been arrested and charged with various crimes, both misdemeanors and felonies. Many former prosectuors turned criminal defense attorneys will brag about their previous efforts at imprisoning people, even for low level offenses.  I attended the University of Texas Law School for the sole purpose of becoming a criminal defense attorney. 

I was fortunate to be hired immediately out of law school by an experienced criminal lawyer and faculty member who had taught me at the University of Texas Criminal Defense Clinic. As a young “baby lawyer” the experience of working with him on both his privately hired cases, as well as court appointments, gave me a broad background in all types of criminal defense, from the lowest level Class C misdemeanors to first degree felonies.

Today, no longer taking court appointments and in private solo practice, I use my ten years of experience in the criminal justice system in and around Austin, Texas to help my clients find solutions to the problems they were never expecting.

When you retain me, you can be assured that I will be the attorney handling your case, not an associate with limited or no experience, not a paralegal or legal assistant, and not some affiliated attorney or law firm in a completely different office.

Bar Admissions:

Licensed to Practice in All State and County Courts in Texas


University of Texas School of Law, Austin, Texas, 1997 J.D.

Texas A&M University, College Station, Texas, 1991 B.A.

Other Interests:

  • Chess, Reading, Playing Guitar and Piano, Poker