By Attorney Patrick Apple
When a driver in North Carolina is stopped on suspicion of DWI or DUI, one of the first steps officers often take is to administer field sobriety tests. These tests are theoretically designed to help law enforcement decide whether to make an arrest, but they are far from perfect in practice. Conditions, health, footwear, and even officer training can all influence performance.
At Kreider Attorneys at Law, we have seen how these tests are used and misused in court. We know how to break down every step of the officer’s process to protect clients from unfair results. It is important to remember that every case is unique, and no firm reveals every strategy it uses.
Purpose and Background of Field Sobriety Testing
The goal of field sobriety tests (FSTs) is to give officers clues about possible impairment before making an arrest. The National Highway Traffic Safety Administration (NHTSA) developed a standardized battery of tests meant to measure balance, coordination, attention, and eye movement. When performed correctly, these tests allegedly can provide limited insight into a driver’s condition. However, when performed incorrectly, which happens often, the results can be misleading.
Courts in North Carolina generally recognize three standardized tests:
- Horizontal Gaze Nystagmus (HGN)
- Walk and Turn (WAT)
- One-Leg Stand (OLS)
Each test has precise instructions that must be followed to be considered valid. Officers receive training through the NHTSA DWI Detection and Standardized Field Sobriety Testing Manual, which outlines every step from start to finish. Yet in practice, officers frequently deviate from those standards.
The Horizontal Gaze Nystagmus (HGN)
The HGN test examines involuntary eye movement caused by alcohol or other central nervous system depressants. The officer asks the driver to follow a stimulus (such as a pen or flashlight tip) horizontally with their eyes. The officer looks for three potential clues in each eye: lack of smooth pursuit, distinct nystagmus at maximum deviation, and onset of nystagmus prior to 45 degrees.
For the results to be valid, the officer must confirm that the driver has no medical conditions that could cause nystagmus, position the stimulus the correct distance from the eyes, and move it at the proper speed. Any mistake, such as moving too quickly, standing too close, or using flashing lights that distract the driver, can invalidate the findings.
An experienced Greensboro DWI attorney should review the body-worn camera footage to verify whether the officer followed protocol. Even subtle errors and environmental conditions can create reasonable doubt about the reliability of the results.
The Walk and Turn (WAT)
The Walk and Turn test measures divided attention, coordination, and balance. The driver must take nine heel-to-toe steps along a straight line, pivot carefully, and return in the same manner while counting each step out loud. The officer looks for clues such as starting too soon, losing balance, stepping off the line, or using arms for balance.
However, the test assumes ideal conditions: a dry, level, well-lit surface and a driver wearing stable footwear. Real roadside conditions rarely meet that standard. Gravel shoulders, uneven pavement, loud traffic, flashing lights, wind, or poor footwear can all create errors unrelated to alcohol.
The officer must also demonstrate the test fully and clearly. If the demonstration or instructions are incomplete, the driver may misunderstand the task, which produces invalid results. Many drivers fail not because they are impaired, but because they are nervous or confused.
The One-Leg Stand (OLS)
The One-Leg Stand test evaluates balance and focus. The driver lifts one foot six inches off the ground and counts for thirty seconds. The officer observes for swaying, using arms for balance, hopping, or putting the foot down.
This test is particularly unfair for drivers with back, knee, ankle, or balance issues. It also becomes unreliable for older drivers, individuals with weight concerns, or those standing on uneven ground. Medical conditions like vertigo or neuropathy can mimic impairment even when no alcohol is present.
A defense attorney can present medical records, witness statements, and even expert testimony to explain why poor performance may have nothing to do with intoxication.
Non-Standardized Tests
Some officers administer non-standardized tests like touching fingers to the thumb, reciting the alphabet, or estimating thirty seconds. These tasks lack scientific validation and vary widely among departments. While they may be used as general observations, they carry little evidentiary weight in court. A skilled North Carolina DWI lawyer can highlight this distinction and show the court that such tests are subjective and unreliable.
Environmental and Personal Factors
The conditions at the roadside often determine the outcome. Cold weather, wet roads, bright lights, flashing lights, heavy traffic, fatigue, stress, or nervousness can all affect performance. Similarly, footwear, injuries, or medical history can change results. A driver in work boots or heels on an incline will perform differently than someone standing on a smooth, level floor.
Experienced attorneys often uses body-worn camera footage to show how environmental conditions made it impossible to perform fairly. In many cases, the footage tells a very different story from what the officer’s report claims.
Using Video Evidence to Expose Inconsistencies
Video evidence is the single most valuable tool in a modern DWI defense. Officers may describe slurred speech, unsteady balance, or confusion, yet the footage might show a calm, cooperative, and steady individual. Even minor differences can change how a judge views credibility.
We review every second of available footage, from the initial stop to the arrest, to identify inconsistencies between the officer’s report and what truly occurred. This approach has helped uncover significant procedural errors that have led to dismissals or favorable outcomes. We often find things that were left out of the report.
How Field Tests Fit into a DWI Case
Field sobriety tests are only part of the State’s case. The results must be combined with other evidence, such as breath or blood test results, driving behavior, and officer observations. If one component fails, the entire case can weaken. Judges evaluate the totality of the evidence, and when one major piece, like field testing, is discredited, the balance often tips toward reasonable doubt. The State must provable all the elements of a DWI beyond a reasonable doubt and field sobriety testing is just a step in their process.
Expert and Cross-Examination Strategies
Cross-examining the officer about field sobriety testing requires preparation and precision. We use the officer’s own training manuals and course materials to question how the tests were conducted. If an officer claims a client “failed,” we can attempt to show that the test was not performed as instructed by NHTSA. In some rare cases, we use expert witnesses with law enforcement training who can explain how improper administration affects accuracy.
These strategies demonstrate to the court that the investigation was incomplete, biased, or inconsistent with professional standards. While not every case results in dismissal, exposing errors strengthens negotiation and can lead to reduced charges or more favorable sentencing.
Common Questions About Field Sobriety Tests
Are field sobriety tests required?
No. They are voluntary. Refusal of field sobriety tests may still lead to arrest, but it cannot by itself prove impairment.
Can I pass if I have a medical issue?
Medical conditions can affect results, but documented history and video evidence can help show the difference between impairment and physical limitation.
Are these tests scientific?
They are only scientific when conducted exactly as trained. Most real-world roadside tests fall short of that standard.
Do officers always follow the manual?
No. Many do not. Body-worn camera video often proves incomplete instructions, missed steps, or incorrect instructions.
Is DWI the same as DUI?
Yes. North Carolina treats both terms identically under N.C.G.S. § 20-138.1.
Final Thoughts
Field sobriety testing is one of the most misunderstood parts of a DWI case. These tests may seem simple, but they are complex evaluations that depend on dozens of small details. When even one of those details is overlooked, the results can mislead both prosecutors and judges. These tests have been described as designed to fail.
At Kreider Attorneys at Law, we approach every DWI by examining those details with precision. We know how to interpret video, how to read between the lines of a police report, and how to expose flaws that others miss. Whether your case involves the HGN, Walk and Turn, One-Leg Stand, or non-standardized tests, we will analyze every angle to build the strongest defense possible.
If you have been charged with DWI or DUI in North Carolina, do not assume the test results are accurate. Contact Kreider Attorneys at Law today at 336-550-1210 to schedule a consultation and discuss your defense strategy.