Nystagmus: Mostly Leave It Alone

Blogging from the Rusty Duncan seminar, and listening to San Antonio DWI lawyer George Scharmen give an excellent presentation on the Field Sobriety Tests yesterday.

One interesting tidbit. Scharmen argued that while of course you must cross the officer about the 6 out of 6 (isn’t it always all 6 clues?) on the Horizontal Gaze Nystagamus, it’s not important to go on and on about it. In fact, it may give it more effect than the jury would otherwise.

Scharmen said – and my notes are skimpy here – he asks about how the officer is only trained by another officer, not a medical professional; impeaches the officer if necessary with the manual where he has made errors in administration, eg. Holding the stimulus for less than 4 seconds at maximum deviation; asks why the results weren’t reproduced for the jury by placing the subject in front of the vehicle to put the HGN on tape, and then…

“I mostly leave it alone”.

[Scharmen asks more than those 3 or 4 questions of course; he’s just saying he deemphasizes it by doing an effective short cross on it where he can.]

Cross Examination: Watch the Witness

One of the purposes of allowing cross examination of witnesses is the idea of confronting your accuser. The theory is that the credibility and sincerity of a witness accusing you is best tested by live cross examination.

A few days ago, while sitting in court waiting for my client’s driver’s license suspension hearing to start, I watched an attorney conduct his cross of the officer who administered field sobriety tests to his client. The lawyer had a list of well prepared questions written out, which he then asked of the officer, one by one. Unfortunately, the method he used was basically to have his head down the entire time, reading the questions off of his legal pad.

When the lawyer got to the part about how the officer administered the HGN test, he had a pretty good line of questions he asked, such as:

            How long did you hold the stimulus at maximum deviation?

            How did you measure nystagmus prior to 45 degrees?

            How many total passes did you make during the HGN?

What the lawyer missed, by burying his head in his notes, was that the officer actually pulled a small “cheat sheet” out of his pocket, which gave him all the “correct” answers to these questions. These apparently weren’t notes from this particular arrest (trust me, no officer would make those sorts of detailed notes on every arrest), but just genereal guideline answers.

Not surprisingly, the officer got all of the questions right. But he was just reading his own pre-prepared notes, probably jotted down right of the NHTSA field sobriety test manual itself.

If the attorney had noticed this, he could easily have asked the officer to testify from his own memory of the event, or at least noted for the record that the officer was reading his answers from a sheet. Because he wasn’t paying attention to the witness, he missed this entirely.

One of the reasons I ask for driver’s license hearings in every DWI case is that it gives me the opportunity to cross examine the stopping and arresting officers. Several times, in cases that otherwise seemed somewhat hopeless, I have found out things about a DWI case that are extremely helpful. One of these things can be as simple as… the officer makes a really poor witness.

Complete and thorough preparation for cross examination is essential, but don’t forget to watch the witness testify. Evaluate his demeanor, and always ask yourself this: “Would this police officer make a good witness in front of a jury?”

What is Nystagmus?

Nystagmus is an actual medical phenomenon that describes an involuntary eye movement, or ‘ a jerking of the eyes’, as police officers often call it. Nystagmus can be difficult to detect, and has multiple causes, other than alcohol consumption.

Unfortunately, diagnosing both the complex medical condition itself, as well as divining its cause, has been boiled down to a few hours of a two and a half day Field Sobriety Test certification class, and taught to police officers across Texas and the United States as the ‘gold standard’ for DWI detection.

I can’t count the number of times I have heard the phrase “the eyes don’t lie” (from prosecutors, police witnesses, and others in law enforcement). Well, the truth is that when it comes to DWI detection, they do.

This blog will attempt to dissect truth from fiction, and to study what nystagmus is, what it isn't, what causes it, and why police officers so often believe that what they saw on the scene of an arrest during a DWI investigation really isn’t science at all. Stay tuned…

Types of Nystagmus: 2006 NHTSA Manual

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: NHTSA Manual 2006

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 Resulting from Neural Activity: NHTSA Manual 2006

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)

Nystagmus Resulting from Pathological Disorders: NHTSA Manual 2006

Nystagmus can be caused by certain pathological disorders. They include brain tumors and other brain damage or some diseases of the inner ear. These pathological disorders occur in very few people and in even fewer drivers.