Field sobriety exercises were validated on people without the conditions that fill an ordinary population, and they are graded by an officer who is not a doctor and who took no medical history at the side of the road. Age, weight, injuries, inner-ear problems, and a range of neurological and eye conditions all affect how a person balances and how the eyes move, and the officer is only giving a lay observation of that performance, not a scientific reading, a line drawn on the HGN as scientific evidence page.
The procedure itself recognizes this. The guidance is that people over about 60, people more than 50 pounds overweight, and people with conditions that affect balance should not be given the walk and turn or the one leg stand, and that people in raised heels should be allowed to remove their shoes. When an officer runs someone through anyway and counts the predictable result as a clue, the clue is an artifact of the wrong test for that person.
The procedure itself excludes several of these from the balance exercises, and many of them produce the eye jerk the officer reads as alcohol. None were screened at the roadside.
The eye test has medical look-alikes
Horizontal gaze nystagmus is presented as a window into alcohol, but the eye jerk it looks for has a long list of other causes. Inner-ear disorders, head injuries, certain prescription and over-the-counter medications, fatigue, and even nystagmus that a person simply has naturally can all produce or imitate it. The officer cannot separate alcohol nystagmus from the rest by watching, and the pre-test checks for equal pupils and resting nystagmus are exactly the steps that get skipped.
| The condition | The clue it mimics |
|---|---|
| Inner-ear or vestibular problem | Swaying, arms out, and stepping off on the balance tests |
| End-position nystagmus, a natural eye jerk | Nystagmus at maximum deviation on HGN |
| Back, leg, knee, or ankle injury | Missing heel to toe, putting the foot down, hopping |
| Age over 65 or 50-plus pounds overweight | Difficulty NHTSA itself said to expect on the balance tests |
| Some common medications | Eye and balance signs an officer cannot tell from alcohol |
The officer runs no medical exam beyond the eye check and is not trained to rule any of these out, so the record simply never asks the question.
Your eyes jerk for reasons that have nothing to do with drinking
The jerking the officer calls a sign of alcohol has a long list of ordinary causes. There is a natural end-position nystagmus that shows up in sober people at the far edge of their vision, documented in Booker, End Position Nystagmus as an Indicator of Ethanol Intoxication, 41 Science and Justice 113 (2001), and there are inner-ear conditions, certain neurological issues, and common medications that produce the same movement. The officer cannot tell one from another by looking, and is not trained or licensed to try. That is the quiet problem with reading a body on the side of a road, because a person is not a machine with one explanation for every reading, and the exercises were never built to sort the sober person with a bad knee or a middle-ear problem from someone who had been drinking.
Balance is a physical task with physical explanations
Standing heel to toe on a line or balancing on one leg draws on the back, the legs, the knees, the ankles, and the inner ear. A bad knee, an old back injury, vertigo, or simply carrying extra weight makes swaying and stepping off the expected result, sober or not. These are not excuses. They are documented physical facts that explain the performance the report blames on alcohol.
Putting the record in front of the jury
Your medical history is evidence. I gather the records, match a specific condition to the specific clues the officer wrote down, and show the jury a documented, innocent reason for what happened. The State still has to prove impairment beyond a reasonable doubt, and a real medical explanation makes that proof a great deal harder.
The first thing I want to know is who you are, because your body is evidence and the officer never looked at it. I gather your history, your medications, your injuries, and anything about your eyes or your ears, and I set it next to the clues the officer wrote down. I know this battery from the inside, so I can show a jury that what got recorded as impairment was your knee, your inner ear, or the simple way your eyes move, and that no one on the roadside ever bothered to ask.
I started out as an Assistant Public Defender in Florida’s Thirteenth Judicial Circuit, in Tampa, and today I am one of six ACS-CHAL Forensic Lawyer-Scientists in Florida and an NHTSA-qualified field sobriety instructor. I was trained to administer this battery and to teach the officers who give it, so I can stand in front of a jury and show the exact point where the roadside exercises in your case left the standard. Learn more about my background.
Questions About Medical Conditions
Can medical conditions affect field sobriety tests?
Yes, strongly. Age, weight, injuries to the back or legs, inner-ear problems, and neurological or eye conditions all affect balance and eye movement, and the officer at the roadside is not a doctor and did not take a medical history.
Who does the procedure say should not be tested?
NHTSA guidance is that people over about 60, people more than 50 pounds overweight, and people with conditions that affect balance should not be given the walk and turn or one leg stand, and that people in heels over two inches should be allowed to remove their shoes.
Can a medical condition cause nystagmus?
Yes. Inner-ear disorders, neurological conditions, certain medications, fatigue, and even naturally occurring nystagmus can all produce or mimic the eye jerk, and an officer cannot tell those apart from alcohol by looking.
What if the officer did not ask about my health?
That is part of the challenge. The exercises were validated on people without these conditions, so grading someone the procedure excludes, or who has an unscreened condition, produces clues that say nothing reliable about alcohol.
Do I have to prove the condition caused the result?
No. The burden stays with the State to prove impairment. A genuine medical explanation for the clues undercuts the State's proof, which is what reasonable doubt is about.
How do you use my medical history?
I gather your records and history, match them to the specific clues in the report, and show the jury an innocent, documented reason for the performance the officer attributed to alcohol.
Related: the one leg stand, HGN as scientific evidence, the roadside conditions, the HGN eye test, and why the results are unreliable.
Can a medical condition make me fail these tests sober?
Yes. Inner-ear problems, back and leg injuries, some medications, and even a natural eye movement called end-position nystagmus can produce the exact signs an officer counts as clues, and NHTSA itself warns that age, weight, and certain conditions cause difficulty. The officer does no medical exam to rule any of it out.
This page is general information, not legal advice, and it does not create an attorney-client relationship. Field sobriety exercises in Florida are governed by case law and by section 316.193, Florida Statutes. Procedures and rules change, and every case turns on its own facts. Past results do not guarantee a similar outcome.
