Nystagmus is an actual medical phenomenon that describes an involuntary eye movement. Police officers often call it "a jerking of the eyes." Nystagmus can be difficult to detect even when the observer is well trained. Additionally, it had 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 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.
I will attempt to dissect truth from fiction, and explain to you 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…