Last week, I explained the clinically designed purpose of the Romberg Balance Test and how in a meaningful way it has never even been facially validated for its intended or purported purpose as a method of recording drug-related impairment in DUID cases, but rather is used as a neurological screening test to rule-out in only a preliminary way brain damage.
In that post I concluded that
Like many tests used at roadside [or in the DRE protocol], the designed and intended use of a legitimate and useful clinical screening test has been literally bastardized and hijacked by police to now be used as a supposed indicator for possible alcohol or drug impaired driving.
With this post, I would like to examine another step in the Drug Recognition Expert (DRE) protocol, the Finger-to-Nose test in the same way to see if the same conclusion is arrived.
We start with a little etomolgy…
Unlike the Romberg Balance test, there is no identified creator of the Finger-to-Nose test. Perhaps it will never be known and will relate back to the age old childhood developmental task of process identification.
However, what is well known is the scores of clinical research published in peer-reviewed treatises that have successfully and validly linked the clinical use of the Finger-to-Nose test to be used as a neurological differential diagnosis tool.
What is a differential diagnosis tool?
The medical term of art "differential diagnosis tool" means that a systematic method is used to identify unknowns.
The term differential derives from the word difference: careful differential diagnosis involves first making a list of possible diagnoses, then attempting to remove diagnoses from the list until at most one diagnosis remains. In some cases, there will remain no diagnosis; this suggests the physician has made an error, or that the true diagnosis is unknown to medicine. Removing diagnoses from the list is done by making observations and using tests that should have different results, depending on which diagnosis is correct.
In other more crude words, it is the process of elimination.
Moreover, and perhaps more importantly, the clinical use of the Standardized Finger-to-Nose test (SFTN) differs substantially from the police officer administered one.
For the police officer administered one, the subject is commanded to stand with his/her arms out horizontally parallel to the ground and in a fashion consistent with making a "T" when one were to look directly ahead at the test subject. He/she will be commanded to keep his or her feet together. Then, remarkably with his/her eyes closed, he/she will then be ordered to take one hand at a time listening to the officer’s command, and place it straight out in front of the subject’s body, then bending the arm directed at the elbow forward, move to touch the tip of the finger to the tip of the nose. Then back to the ready "T" position to repeat. [Editor’s note: Please refer to the comments section of this post to see the complete comment and reply between myself and Thomas Page for a full discussion into the correct and incorrect test administration- a thank you to Mr. Page for helping me make a complete and wholly accurate post.]
Some of the problem with the DRE variation of the Finger-to-Nose test is in the explanation. One of the instructions is for the test subject is to use only the tip of his/her index finger to touch the nose. Most people, even sober people, misinterpret this instruction and use the pad of the finger as a substitute.
Here is the clinically valid administration of the Finger-to-Nose test.
-Justin J. McShane, Esquire, Pennsylvania DUI Attorney
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