DUI Attorney on Field Sobriety Tests: What the Police Don’t Tell You

Most people first hear the phrase “field sobriety tests” on a dark shoulder of the highway, blue and red lights bouncing off the guardrail. You’re tired, anxious, and counting the minutes. An officer asks you to step out, then runs through a script: follow my pen, walk this line, stand on one leg. What they don’t say is just as important as what they do. After years defending DUI and DWI cases, I’ve seen how those roadside rituals carry outsized weight in court, even though the science is limited and the conditions are often stacked against you.

This is not police-bashing. Traffic stops are tense and unpredictable, and most officers are doing the best they can. But fairness requires an honest account of what field tests can and cannot show, how they’re supposed to be given, and why small deviations matter. If you’re facing a DUI, the early choices and the paper trail created by those tests often shape the whole case.

What roadside tests really measure

The National Highway Traffic Safety Administration, or NHTSA, promotes three “standardized” field sobriety tests when administered exactly as trained: the Horizontal Gaze Nystagmus, the Walk and Turn, and the One Leg Stand. The agency’s research, much of it from the late 1970s and 1980s with later refinements, suggested a correlation between performance on those tests and blood alcohol concentration. Even under controlled conditions, the accuracy rates aren’t perfect. In the real world, roadside conditions vary wildly.

What these tests largely measure is a blend of balance, divided attention, and eye movements. They are not IQ tests and they are not sobriety meters. Anxiety, fatigue, footwear, road slope, age, weight, inner-ear issues, back or knee injuries, and language barriers all pull on the results. Officers are trained to ask about some of these factors, but I often see them glossed over or omitted in reports.

Two practical truths follow. First, the tests aren’t designed to identify sober drivers, only to detect impairment. That means a nervous or clumsy but sober person can fail. Second, minor errors in instructions or scoring by the officer matter because the tests are “standardized.” Deviation from the method chips away at reliability. In the courtroom, that crack can become reasonable doubt if developed correctly by a seasoned DUI attorney.

The three standardized tests, stripped to their essentials

The Horizontal Gaze Nystagmus, or HGN, looks for involuntary jerking in the eyes as they track a stimulus, usually a pen or small flashlight. The officer holds it a short distance from the face and moves it at particular speeds and distances, while the subject follows with their eyes, not their head. Nystagmus does occur more readily with alcohol, but several medical conditions and some medications can increase it too. An officer who hurries the passes, holds the pen too high or too low, or tests on the shoulder of a road with strobe-like lights can generate artificial “clues.” Most jurors don’t know how sensitive HGN is to technique and environment, and many defense attorneys, frankly, skip the cross-examination required to show that.

The Walk and Turn requires a specific instruction phase followed by nine heel-to-toe steps along a straight line, a pivot, and nine steps back. The subject must keep hands at sides and count aloud, all while maintaining balance. On video, you’ll often see a gravel shoulder, a painted seam that curves, or no actual line at all. People try to do their best, but the test penalizes raising arms, stopping to steady, starting too soon, miscounting, or not touching heel to toe. Add boots, dress shoes, or heels, a cold wind, and adrenaline, and the scoring turns harsh fast.

The One Leg Stand involves lifting one foot a few inches off the ground and counting for about 30 seconds. It punishes swaying, hopping, putting the foot down, or using arms for balance. Again, age, weight, injury, and surface conditions are major factors. The methodology assumes a level, dry, non-slippery surface and minimal distractions. I can count on one hand the number of dwi attorney suffolk county roadside scenes that meet that description.

When officers steer you into these tests, they are already gathering evidence. Everything from how you exit the car to your tone of voice gets folded into the arrest decision. Once you know that, the roadside dance looks less like a neutral evaluation and more like an evidence collection sequence. A good criminal defense attorney will dissect each moment to show jurors the human factors the police report forgets.

What you’re not told at the roadside

You don’t have to do field sobriety tests. In most states, there is no legal penalty for refusing the physical tests. Refusing may influence the officer’s arrest decision, but there is a world of difference between an arrest and a conviction. What trips people up is the tone of a “request” that feels like a command. If you are not sure, ask directly whether the tests are voluntary. Officers are trained to persuade you to comply, often by framing it as a chance to prove you’re fine. Be aware of the optics and the legal consequences before you nod along.

Another point you won’t hear: roadside tests are not designed for people with certain medical or physical conditions. If you have vertigo, neuropathy, back or leg injuries, or take medications that affect balance, say so. If English is not your primary language, say so. If you are over 65 or more than 50 pounds overweight, NHTSA’s own materials recognize limitations on the balance tests. Officers rarely volunteer that context. Their forms usually have a brief medical section, and a quiet “No issues” box is easy to check after the fact unless you clearly state the problem.

Finally, you won’t be told that slight variances in instructions can transform your performance. Officers must demonstrate the Walk and Turn and One Leg Stand precisely. If they rush the demonstration, fail to confirm you understand, or set the test on a sloped, gravelly shoulder, the validity shrinks. The same applies to HGN, which requires specific distances, speeds, and timing. That level of rigor rarely survives a windy night next to fast traffic.

When the camera sees more than the report

Body-worn and dash cameras changed these cases. Before video, the officer’s narrative drove the outcome, and judges gave wide deference to field observations. Now, jurors can watch. They can see the seam of the road used as a line, hear the officer’s cadence, and watch how closely you follow instructions. I’ve had cases where the report lists six of eight HGN “clues,” but the video shows a stimulus held too high with rapid passes that almost guarantee nystagmus in healthy eyes. I’ve had Walk and Turn videos where the instruction phase is drowned out by the roar of trucks, then the report marks “started too soon” despite the officer gesturing to begin.

This is where a focused DUI attorney earns their fee. We freeze the video, measure distances, track the officer’s timing, compare to NHTSA manuals, and show where the process broke. The point is not to nitpick, it is to restore the presumption of innocence by revealing how context affects performance. When jurors see an honest effort on a poor surface in cold wind, they hesitate to equate wobble with intoxication.

The breath test haze around the field tests

Officers often couple field sobriety tests with a roadside breath device. Laws differ between states, but two categories matter: preliminary breath tests at the scene, which are typically less reliable and are sometimes inadmissible except to justify arrest, and evidentiary breath tests at the station, which carry more legal weight. Many drivers think the roadside breath device is mandatory because of “implied consent.” In most places, implied consent laws attach to the evidentiary test after a lawful arrest, not the portable device at the curb. Refusing the station test can trigger license suspensions, sometimes severe, but refusing the curbside test may not carry the same penalties. The distinction is critical, and the officer is under no obligation to clarify it in plain speech.

Consider a common pattern. The officer stops you for drifting over the line twice. You hand over documents slowly, your eyes look glassy on video, and your voice is thick from allergies and a long day. You fumble a word, and the officer asks you to step out. After the three tests on a sloped shoulder, you give a portable breath sample that reads a number you never see but the officer says indicates alcohol. You are arrested and later at the station the evidentiary breath test reads just over the limit. A thorough defense may show that the driving pattern was ordinary, the roadside tests were corrupted by surface and footwear, and the portable reading was not a reliable indicator. If the evidentiary result is close to the line, that context can make or break suppression motions or how a jury perceives “beyond a reasonable doubt.”

The role of medical and non-alcohol explanations

One of the most powerful tools in these cases is a simple timeline. When did you last eat and what did you eat? What is your height and weight? Do you have diabetes or hypoglycemia? Do you experience acid reflux? Are you on medications for anxiety, seizures, allergies, or ADHD? Have you had any recent head injuries? Did you work a double shift? Did you wear contacts that dry out in wind? A skilled criminal defense attorney will ask these questions because they feed plausible, provable reasons for poor test performance that have nothing to do with impairment.

There are well-known scientific concepts at play. Mouth alcohol can skew some breath readings when reflux or recent drink residue exists. Fatigue and sleep deprivation degrade divided attention similar to moderate alcohol. Certain neurological conditions cause baseline nystagmus. Anxiety will change breathing and cadence, and can cause slight tremors that read as “sway.” You do not need a stack of medical records to show this, but corroboration helps: a prescription label, a coworker’s note about your shift length, even photos of your shoes that night.

Where officers commonly depart from the manual

No one’s perfect on the side of the road. Yet pattern errors show up again and again.

Incomplete instruction phase: The officer fails to verify you can hear and understand, especially near traffic noise, or skips key phrases like “don’t begin until I tell you to start” but later dings you for “starting too soon.” Improper HGN technique: The stimulus is too close or too high, passes are rushed, there is no check for equal pupil size and equal tracking, or the test happens with flashing lights in the field of view. Poor surface and footwear: The test is set on gravel, a grade, or in rain, and there is no accommodation for boots, dress shoes, or heels. The manual contemplates a reasonably dry, level, nonslippery surface. Divided attention overload: Rapid-fire instructions with interruptions and questions in between, then scoring you for forgetting a step. Overcounting “clues”: Calling minor foot gaps a miss on heel-to-toe when the spacing is within an inch, penalizing a raised arm that never passes six inches, or double-counting a single misstep.

Those may sound technical. In a courtroom, they are not. They go to whether the government followed its own rules before using subjective tests to convict.

How a defense lawyer attacks flawed field tests

When clients come in after a DUI arrest, we do not start with speeches about rights. We start with materials and time. We obtain body camera and dash video, radio logs, the officer’s training records and certification dates, NHTSA training materials, calibration logs for breath devices, and any incident photos. Then we build a moment-by-moment timeline against what the manual requires.

An example: a client in his fifties, no prior record, stopped for a tag light. The officer thought he smelled alcohol. The Walk and Turn happened on a gravel turnout. The client wore steel-toe work boots. Video showed the officer demo a turn with a pivot that wasn’t per the manual, then criticizing the client for using that same pivot. On the One Leg Stand, the client swayed and touched the foot down once with a gust of wind. The HGN was done with a flashlight in the eyes and short, fast passes. The station breath test read 0.08 to 0.09 on two attempts. We retained a retired traffic enforcement instructor to explain proper technique and environmental limitations, then filed a motion challenging probable cause and sought to exclude the HGN. The judge allowed the case to go to trial but excluded the HGN testimony because the steps were not followed. The jury hung, and the case later resolved to a non-alcohol traffic infraction.

Results vary. Not every case is beatable, and some clients are genuinely impaired. Still, narrowing the case to trustworthy evidence is the attorney’s job. Even when a conviction is likely, a stronger challenge often produces better outcomes, from reduced charges to gentler sentencing.

Should you ever decline the tests?

There is no one-size-fits-all answer. Factors include your state’s laws, your physical condition, your exposure to license penalties, and how much you’ve had to drink. People decline for different reasons: language barrier, knee problems, fear of humiliation on camera, or on counsel’s general advice. Officers may arrest anyway. But if your balance is poor on a good day, you are exhausted, or you’re wearing shoes that don’t belong on gravel, performing the tests can hand the state a highlight reel. On the other hand, a truly sober driver with athletic balance and clear speech might breeze through and avoid arrest altogether.

A measured approach helps. If you choose to decline, say so respectfully and succinctly. Ask if the tests are voluntary. If yes, you can politely refuse physical tests and request a chance to speak with a lawyer at the earliest lawful moment. Remember that in many places, refusing the post-arrest evidentiary breath or blood test carries automatic license consequences, sometimes severe and immediate. Those consequences can outweigh the risk of a borderline reading. When in doubt, a quick call to a criminal attorney experienced in DUI or a traffic ticket attorney who handles DWI stops can prevent reflex mistakes. Not every agency allows calls at roadside, but asking can matter.

The hidden cost of a split-second misstep

A DUI arrest touches more than your criminal record. Professional licenses, insurance rates, immigration status, and employment can change on a single conviction. For commercial drivers, even a first-time DWI can sideline a career. If your life intersects with other areas of criminal law, the stakes multiply. People on probation for unrelated matters, whether a Drug Crimes attorney or a Domestic Violence attorney helped you months ago, can see probation violations based on an arrest alone. If you have a pending case under a White Collar Crimes attorney or a Fraud Crimes attorney, a new arrest may affect bail. The criminal system does not silo your cases the way you might hope.

That is why the front end of a DUI case deserves real attention. Waiting until arraignment to think strategically is a missed chance. Early evidence requests, scene photos before conditions change, and quick medical consultations can reshape the narrative that lands on a judge’s desk.

Building a record that reflects your reality

Defending a DUI is not just poking holes. It is telling a credible story grounded in specific facts. A good dwi attorney will ask you for details you might find trivial: what you ate and when, the route you took, the music volume, the seat position, the exact shoes you wore, whether your eyes were irritated by contacts, and how long you had been awake. We’ll ask for timestamps from receipts, toll records, or parking stubs. If you work night shifts or suffer sleep apnea, a letter from your doctor helps. If English is your second language, we may bring that to a judge’s attention to contextualize your responses on video.

This process also means confronting the bad facts. If you admitted to “a few drinks,” we need the size, strength, and timing. If you stumbled, we need to know if the gravel rolled under your heel or if you had an old ankle sprain. The worst surprises in court are the ones your own lawyer didn’t hear first.

A reality check on prosecutors and plea negotiations

Prosecutors see hundreds of DUI cases each year. They get used to the same defense themes. What cuts through is specifics backed by evidence. A prosecutor is more likely to reconsider if the video and the manual show clear procedural missteps, if a medical letter explains an eye condition affecting HGN, or if footwear and surface conditions are documented. This is also where broader criminal defense experience matters. A criminal defense attorney who negotiates daily on Assault and Battery, theft cases from a petit larceny attorney, or even work with a gun possession attorney or drug possession attorney learns the local norms, the personalities, and which arguments move the needle. The same skill translates to DUI.

The aftermath: license hearings, ignition interlocks, and long-term planning

Many states split a DUI into two tracks: criminal court and administrative license proceedings. The deadlines for challenging a license suspension can be tight, sometimes within 10 to 15 days of arrest. If you miss that window, your license can be suspended automatically, even if the criminal case later gets dismissed. An experienced traffic violations attorney can file the challenge, secure a hearing, and sometimes avoid a pretrial suspension.

If an ignition interlock device becomes part of your future, get to know how it works. False positives happen with mouth alcohol from certain foods or mouthwash. Plan your mornings to allow warm-up time and a second test if needed. Keep logs. Small, diligent habits make the difference between a clean compliance record and a stack of violation notices.

What to do in the five minutes that matter most

A roadside stop unfolds fast. Clear, calm decisions help. The following brief checklist is practical, not theoretical:

Pull over safely, turn off music, lower windows if safe, and keep hands visible on the wheel. Gather documents only when asked. Be polite and brief. You must provide license, registration, and proof of insurance. You do not have to answer questions about where you’ve been or how much you drank. If asked to exit, comply. Ask if field sobriety tests are voluntary. If yes, decide based on your condition, footwear, and surface. If you decline, do so respectfully. If offered a roadside breath test, know your state’s rules. Politely ask whether refusal carries license penalties at that stage. If uncertain, state you wish to consult a lawyer as soon as permitted. If arrested, do not argue. At the station, implied consent laws likely apply. Weigh the license consequences of refusing the evidentiary test. Request to contact a dui attorney or criminal attorney promptly.

Practicing these steps ahead of time keeps panic from taking over when you least need it.

How jurors think about field tests, and how to help them

Jurors bring common sense into the box. If the video shows a respectful driver doing their best on a sketchy surface in boots, they question a report that paints disaster. If the officer’s instructions are clear, the surface is good, and the performance is sloppy across the board, they lean toward impairment. That means your case hinges on details and clarity. The defense should simplify technical points without underestimating jurors. For HGN, a precise analog helps: we explain that the test is like using a thermometer that must be held at a certain distance and time, not waved around. If used wrong, it reports a fever that isn’t there.

When jurors understand that standardized means method-dependent, they start to see the difference between careful science and a rushed roadside approximation. That gap is where reasonable doubt lives.

Where field tests intersect with other charges

Sometimes a DUI stop snowballs. A search after arrest turns up a lawfully owned firearm, but local transport rules were not followed, drawing a weapon possession attorney into the case. Or an old prescription bottle raises drug possession attorney issues when pills are loose. If a heated exchange with an officer leads to an extra count like criminal contempt or a criminal mischief attorney allegation over a damaged divider in the holding cell, coordination becomes crucial. The same stop can even tumble into unrelated matters if a passenger has warrants, or if items in the car create suspicion of theft under a petit larceny attorney lens. A robust defense team that can coordinate among a gun possession attorney, a Theft Crimes attorney, or a Drug Crimes attorney helps protect you from unintended spillover.

On rare occasions, an allegation from the stop setting spirals into serious territory. A fight on the scene could spawn an Assault and Battery attorney issue. Unlikely but possible claims can include Aggravated Harassment, trespass, burglary, or even robbery if police believe property was involved earlier in the night. While these tend to be stretch charges tied to separate events, the video and timeline from the DUI stop still matter. They can corroborate or contradict later claims. A defense lawyer with broad experience across Grand Larceny, embezzlement, and White Collar Crimes understands how prosecutors build multi-count narratives and how to keep your DUI limited to what actually happened.

What the police don’t say out loud

Field sobriety tests create a visual story. Officers know that a jury seeing you step off an imaginary line plays differently than reading a BAC number alone. They know that many people have no idea the tests are optional or that conditions matter. They know that if you try to talk your way out of it and keep chatting, nervous speech patterns can sound like intoxication on video. And they know most drivers won’t ask whether a particular test is voluntary or whether the surface is acceptable.

None of that is sinister. It is human. But the law promises a higher bar before you lose your license, your livelihood, and your record. The best antidote is preparation, not bravado. Know your rights. Understand the limits of the tests. Remember that politeness and clear, brief communication do more for you than roadside arguments.

If you are reading this after an arrest, time is not your friend. Preserve the facts while they are fresh. Write your own timeline, including meals, routes, and any medical details that might matter. Photograph shoes and clothes. If you can return safely to the scene, capture the slope, lighting, and line you walked. Then call a dui attorney with real trial experience, not just a plea mill. Ask about their approach to body cam review, their comfort cross-examining HGN, and their track record with suppression motions. The difference between a conviction and a second chance often lies in the space between what you were told and what the law actually requires.

Michael J. Brown, P.C.
(631) 232-9700
320 Carleton Ave Suite No: 2000
Central Islip NY, 11722
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