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I will continue on today with some of the factors to consider in a dui case, and some of the test the police use.  I  will continue with some of the test the police will use to determine if there is probable cause to arrest somoene for DUI. 


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.  This could be observed in a person after a rollover accident.  or spin out.



occurs when a foreign fluid such as alchol that alters the specific gravity of the blood in unequel concentrations in the blood and the vesitbular system.  This  causes the vestibular system to respond to gravity in certain positions, resulting in nystagmus.


PAN I occurs when the inner ear alcohol concentration in the blood is greater than the inner fluid.  PAN occurs while the BAC is increasing. 

PAN II occurs when the alcohol concentration in the inner ear.  This occurs while the BAC is decreasing. 



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 include watching strobe strobe lights, rotating lights, or rapidly moving traffic.

Physiosocial Nystagmus is a natural nystagmus that keeps the sensory cells of the eye from tiring.  This is the most common type of Nystagmus this produces extremely minor jerks of the eyes. 

Natural Nystagmus

Gaze Nystagmus is a form of nystagmus that occurs when the eyes attempt to maintain visual fixation on a stimulas. Horizontal, vertical, and resting nystagmus are three forms.

Pathological Disorders

Nystagmus can also be caused by patholigical disorders.  They include brain tumors and other brain damage and some diseases of the inner ear. 


Certain medical conditions may also cause nystagmus to be present. 

Officers are trained to look for a total of six clues on the HGN test.  The officer looks for the same three clues in each eye.  If four or more clues are observed the test meet the criterion and or is a failure of the test.


A look of smooth pursuit clue number one.  this clue is present if the eyes jerk or bounce as they follow smoothly moving stimulas.

Distinct and sustained nystagmus at maximum deveation clue number 2 this clue is evident if the eye is held at maximum deviation of four seconds and continues to jerk toward the side some people exhibit jerking of the eye at maximum deviation even they are not imparied. 

Difference between Distinct Nystagmus and Distinct and Sustained Nystagmus at Maximum Deviation Questions. 

In the next article I will continue wiht a discussion of the tests to determine if someone is unde the influence while driving.

Gerald Schwab, Jr.


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