A Maryland field sobriety test is not as objective as it looks. You’re standing on a sloped road shoulder at 11 p.m., wind in your face, headlights behind you, nerves running high — and an officer is scoring your every movement against a checklist. Environmental conditions, physical health, and officer error can all produce a false “fail” on a perfectly sober person. If you’ve been charged with DUI in Rockville or anywhere in Maryland based on field sobriety test results, those results can be challenged — and challenged successfully.
Attorney Michael Taylor explains exactly how.
What Are the Standardized Maryland Field Sobriety Tests?
The National Highway Traffic Safety Administration (NHTSA) developed three tests considered “standardized” for DUI detection — meaning they must be administered in a consistent, prescribed manner every single time:
- Horizontal Gaze Nystagmus (HGN) — tracking involuntary eye movement as you follow a stimulus
- Walk-and-Turn (WAT) — nine steps heel-to-toe, turn, nine steps back
- One-Leg Stand (OLS) — stand on one foot, count aloud, hold for 30 seconds
Courts accept these tests as evidence — but only when administered exactly as NHTSA protocols require and only under appropriate conditions. When either standard isn’t met, the Maryland field sobriety test results are unreliable and legally challengeable. According to the NHTSA Standardized Field Sobriety Testing Student Manual, even minor deviations from protocol compromise the validity of results.
Environmental Factors That Cause False Fails on a Maryland Field Sobriety Test
The NHTSA’s own manual requires tests to be conducted on a dry, hard, level, non-slippery surface. Maryland roadsides almost never meet that standard perfectly.
Uneven or Sloped Pavement
Road shoulders are designed to slope for drainage — which means standing on them shifts your center of gravity. A “sway” or “step off the line” scored by an officer during the One-Leg Stand or Walk-and-Turn Maryland field sobriety test may simply be your body compensating for uneven ground. Gravel, cracked asphalt, painted lines, and debris compound the problem further.
Wind, Weather, and Lighting
Wind gusts directly affect balance during the One-Leg Stand. Cold temperatures cause muscle stiffness. Rain creates slippery surfaces. Darkness removes the visual cues humans rely on for equilibrium. Flashing patrol car lights — positioned directly behind most subjects — are a documented source of disorientation that NHTSA protocols acknowledge but officers routinely ignore.
Traffic Noise and Anxiety
Multi-step instructions delivered roadside while highway traffic passes at speed creates significant cognitive load. Anxiety alone — in a completely sober person — can impair the divided-attention tasks these tests measure. An anxious sober person and an impaired person can produce identical test performances.
Physical Conditions That Invalidate Maryland Field Sobriety Test Results
This is where many challenges are most powerful. The NHTSA manual explicitly lists medical and physical conditions that officers must account for before administering and scoring these tests.
Inner Ear Disorders
The vestibular system — located in the inner ear — is the body’s primary balance mechanism. Conditions including BPPV, labyrinthitis, Ménière’s disease, and chronic ear infections cause balance impairment entirely unrelated to alcohol. A person with an inner ear disorder may be completely sober and still fail the OLS or WAT. NHTSA protocols require officers to ask about such conditions beforehand — failure to do so directly undermines the Maryland field sobriety test results.
Prior Injuries and Orthopedic Conditions
Ankle sprains, knee surgeries, hip replacements, back injuries, and leg conditions affect balance and gait in ways that produce false fails on the Walk-and-Turn and One-Leg Stand. The NHTSA manual specifically notes that individuals 65 or older, or those 50+ pounds overweight, may struggle with these tests for purely physical reasons. Per the NHTSA’s DWI Detection guidelines, these factors must be considered before scoring.
Neurological Conditions and Medications
Multiple sclerosis, Parkinson’s disease, peripheral neuropathy, and traumatic brain injury directly affect balance, coordination, and gait. Prescription medications — including those treating the above conditions — can cause dizziness or balance impairment unrelated to alcohol. If the officer did not ask about medications or medical history before administering the test, the results are compromised.
Footwear
NHTSA protocols specifically require officers to offer subjects wearing heels over two inches the opportunity to remove them before performing the Walk-and-Turn or One-Leg Stand. If that offer wasn’t made, that’s a direct protocol violation.
Officer Error: When the Maryland Field Sobriety Test Isn’t Actually Standardized
Beyond subject-specific factors, the officer’s own administration is frequently flawed. NHTSA training requires officers to:
- Demonstrate each test before asking the subject to perform it
- Use specific scripted verbal instructions — any deviation invalidates standardization
- Score only prescribed clues — HGN has six, WAT has eight, OLS has four; minimum thresholds must be met
- Ask about physical and medical conditions before administering any test
- Ensure suitable surface and conditions before beginning
Officers who skip demonstrations, improvise instructions, fail to ask about medical conditions, or administer tests on unsuitable surfaces produce results that are not scientifically valid. An experienced DUI defense Rockville attorney will obtain the officer’s NHTSA training records, dashcam and bodycam footage, the arrest report, and the charging documents — then compare every step against what the protocol actually requires. Discrepancies are more common than prosecutors want juries to know.
What to Do After a Maryland Field Sobriety Test
If you were given field sobriety tests during a Maryland traffic stop, act immediately:
- Write down everything — road conditions, lighting, weather, exact instructions given, your physical condition at the time
- Note any injuries, medications, or medical conditions that may have affected performance
- Do not assume the results are unbeatable — they are regularly challenged and suppressed
- Contact a DUI defense attorney before your court date — dashcam footage and arrest records must be obtained before they are overwritten or sealed
For context on how the legality of the traffic stop itself affects everything that follows, see our guide on Determining Probable Cause: Your Rights During a Maryland Traffic Stop. For the full picture of what a conviction means beyond the courtroom, read The Lasting Impacts of a DUI Conviction in Maryland.
Call the Law Office of Michael A. Taylor at 301-251-2772 or contact us here for a consultation.
