“Designed for Failure”: Why You Can’t “Pass” a Field Sobriety Test

By: John Guidry

Every part of a DUI arrest must be examined to provide an excellent defense, and I’ve been doing just that since 1993. No discussion of DUI defense is complete without talking about Field Sobriety Tests (FSTs).

• The Reality: Just because an officer sees you driving away from a bar late at night and stops you for weaving, that doesn’t automatically give them the right to make you walk the line.
• The Law: An officer needs Reasonable Suspicion of criminal activity (impairment) to request these tests.
  • “Probable cause for a DUI arrest must be based upon more than a belief that a driver has consumed alcohol; it must arise from facts… that show a probability that a driver is impaired.” – State v. Kliphouse

Did you “fail” the roadside gymnastics?

These tests are designed to make you look drunk. Call John today at (407) 423-1117.

The Flaw: “Divided Attention” vs. Normal Faculties

FSTs are not designed to test your “Normal Faculties.” They are Divided Attention Exercises designed to overload your brain.

• The Goal: They force you to do two things at once (balance physically while processing mental instructions).
• The Problem: Normal abilities are well-learned skills (like walking). FSTs are unnatural movements.
• The Trap: Officers use the words “Pass” and “Fail” to mislead the jury. These are not scientific tests; they are “exercises.” If the proper scientific predicate isn’t laid (and it rarely is), we fight to stop the jury from hearing the word “Test.”

The Exercises: Walk & Turn and One Leg Stand

We are going to review two of the most popular tests (aside from the Eye Test). Crucial Rule: These tests require a flat, hard, dry, and level surface with adequate lighting.

• Who is Exempt? People over 65, people 50+ pounds overweight, or those with back/leg/middle ear problems are NOT candidates for these tests. If the officer made you do them anyway, the results are invalid.

1. The Walk and Turn (W&T)

• The Procedure: 9 heel-to-toe steps on a line, turn around (keeping one foot on the line), and take 9 steps back.
• The Clues: The officer looks for 8 specific mistakes, including:
  • Starting before told to begin.
  • Stopping to steady yourself.
  • Missing heel-to-toe (even by half an inch).
  • Using arms for balance (raising them more than 6 inches).

2. The One Leg Stand (1LS)

• The Procedure: Raise one leg 6 inches off the ground and count (“1001, 1002…”) until told to stop.
• The Clues: Swaying, hopping, using arms for balance, or putting the foot down.
  • Scientific Fact: In studies of completely sober people, practically everyone swayed and used their arms. How can that be a clue of impairment if sober people do it too?

The “False Positive” Nightmare

Do FSTs actually predict impairment? Not really.

• The Stats: One Florida study found that the Walk & Turn had a 52% False Positive rate and the One Leg Stand had a 40% False Positive rate.
• The Meaning: The officers conducting these tests were wrong about the suspect’s impairment nearly half the time.
  • Comparison: Could you imagine a cancer test or pregnancy test being wrong 50% of the time? Yet citizens are arrested daily based on this “Voodoo Science.”

John’s 2026 Update: AI Motion Tracking & Smart Watches

Note: In the past, the officer “estimated” your sway. In 2026, the computer measures it.

1. AI Body Cam Analysis In 2026, prosecutors use “Motion Analysis Software” on Body Cam footage.

• The Tech: The software places a digital skeleton over your body in the video and calculates your “Sway Angle” and “Step Variance.”
• The Threat: They present this as “Objective Data.” “The defendant swayed 12 degrees to the left.”
• The Defense: We argue that the Body Cam lens (often fisheye) distorts the image. We subpoena the algorithm to prove it wasn’t calibrated for a roadside environment with uneven gravel and flashing lights.

2. Smart Watch Subpoenas Did you realize your Apple Watch or Garmin records your balance?

• The Trap: Police are now seizing Smart Watches incident to arrest.
• The Evidence: They look at the accelerometer data during the One Leg Stand. If your watch shows high variability or a spike in heart rate, they use your own device to prove “Loss of Physical Control.”
• The Defense: These consumer devices are not forensic tools. We file motions to exclude this data because a Fitbit is not a certified breathalyzer or balance beam.

3. “Virtual Reality” Jury Views Since the tests require a “flat and level surface,” we now use LiDAR scans of the roadside.

• The Strategy: We show the jury a 3D model of the ditch or slanted shoulder where you were forced to perform. When the jury sees you were asked to balance on a 15-degree slope, the “failure” is easily explained by gravity, not alcohol.

Don’t Let Them “Grade” You

If you haven’t been drinking, or even if you have, these tests are designed for you to fail. We know the science (and the lack thereof) behind every step.

Call me at (407) 423-1117. Let’s grade the officer.

About John Guidry II

John Guidry II is a seasoned criminal defense attorney and founder of the Law Firm of John P. Guidry II, P.A., located in downtown Orlando next to the Orange County Courthouse, where he has practiced for over 30 years. With more than three decades of experience defending clients throughout Central Florida since 1993, Guidry has successfully defended thousands of cases in Orange, Seminole, Osceola, Brevard, Lake, and Volusia counties. He has built a reputation for his strategic approach to criminal defense, focusing on pretrial motions and case dismissals rather than jury trials.

Guidry earned both his Juris Doctorate and Master of Business Administration from St. Louis University in 1993. He is a member of the Florida Bar and the Florida Association of Criminal Defense Lawyers. His practice encompasses the full spectrum of Florida state criminal charges, with a particular emphasis on achieving favorable outcomes through thorough pretrial preparation and motion practice.

Beyond the courtroom, Guidry is a prolific legal educator who has authored over 400 articles on criminal defense topics. He shares his legal expertise through his popular YouTube channel, Instagram, and TikTok accounts, where he has built a substantial following of people eager to learn about the law. His educational content breaks down complex legal concepts into accessible information for the general public.

When not practicing law, Guidry enjoys tennis and pickleball, and loves to travel. Drawing from his background as a former recording studio owner and music video producer in the Orlando area, he brings a creative perspective to his legal practice and continues to apply his passion for video production to his educational content.