When you encounter law enforcement on suspicion of Driving While Intoxicated (DWI), you may be asked to perform a series of roadside evaluations known as Standardized Field Sobriety Tests (SFSTs). These tests are pivotal tools for officers, designed to assess a driver’s balance, coordination, and ability to follow instructions under divided attention, providing crucial indicators of potential impairment. But what exactly are these tests, how are they administered, and perhaps most importantly, can their results be challenged in court?
Understanding these tests is crucial if you ever find yourself in such a situation. While they are standardized, their execution and interpretation are not infallible, and their validity can indeed be questioned.
The Foundation: NHTSA Guidelines
The Standardized Field Sobriety Tests are not arbitrary roadside requests. Their guidelines originate from the National Highway Traffic Safety Administration (NHTSA), a U.S. federal agency under the Department of Transportation. NHTSA embarked on extensive research in the 1970s, which led to the development and validation of these specific tests. The goal was to create a reliable, consistent, and scientifically sound battery of tests that police officers nationwide could use to determine probable cause for a DWI arrest.
NHTSA’s rigorous validation studies ensure that when administered correctly, these tests offer a reasonable correlation to a driver’s Blood Alcohol Concentration (BAC). The agency publishes official training manuals, instructor guides, and participant resources that meticulously outline the standardized procedures. These documents are publicly available and form the backbone of DWI investigation training across law enforcement agencies in the United States. Police departments nationwide integrate these NHTSA standards into their state-specific training programs, aiming for uniformity and reliability in DWI enforcement. The adherence to these precise guidelines is paramount, as any deviation can undermine the test’s integrity and, consequently, its legal standing.
How Officers Administer the Standardized Field Sobriety Tests
For the SFSTs to be considered reliable evidence, officers must follow precise, standardized procedures under ideal conditions. This means the testing surface should ideally be dry, level, and non-slippery, with good lighting and a safe environment free from distractions. Any deviations from these ideal conditions—such as extreme weather, an uneven surface, or the subject’s physical limitations (e.g., age over 65, pre-existing injuries, or high heels)—must be meticulously noted by the officer, as these factors can significantly impact performance.
The tests are typically administered in a specific sequence, beginning with clear verbal instructions and often a demonstration by the officer. During the tests, officers are trained to observe for specific “clues” of impairment, which, when present in sufficient numbers, indicate a probable BAC at or above 0.08%. While NHTSA data suggest accuracy rates of about 88% for HGN, 79% for WAT, and 83% for OLS when used together, these figures assume strict adherence to protocol and ideal conditions.
Let’s delve into each test:
1. Horizontal Gaze Nystagmus (HGN)
This is often the first test administered and is considered the most accurate of the three. It assesses for involuntary jerking of the eyes (nystagmus), which alcohol and certain central nervous system depressants exaggerate.
Administration Procedures:
- Initial Setup: You will be positioned with your feet together, hands at your sides, and instructed to keep your head still.
- Stimulus Presentation: The officer will hold a small stimulus (like a pen or fingertip) 12-15 inches from your nose, slightly above eye level.
- Instructions: You will be told, “Keep your head still and follow this stimulus with your eyes only until I tell you to stop.”
- Initial Check: The officer will first check your eyes for equal pupil size, resting nystagmus (jerking even when not moving), and equal tracking as the stimulus moves side to side quickly.
- Clue Assessment: The officer performs specific passes for each clue, starting with your left eye, typically with at least two passes per eye per clue:
- Lack of Smooth Pursuit: The stimulus is moved smoothly side to side (taking about 2 seconds to move from the center to the maximum deviation point). The officer observes if your eyes jerk instead of following smoothly.
- Distinct and Sustained Nystagmus at Maximum Deviation: The stimulus is moved to the farthest side point (where no white is visible in the corner of your eye) and held for at least 4 seconds. The officer looks for clear, ongoing jerking.
- Onset of Nystagmus Prior to 45 Degrees: The stimulus is moved slowly (about 4 seconds) toward a 45-degree angle from the center. The officer stops and verifies if jerking begins before your eyes reach this angle.
- Vertical Gaze Nystagmus (Optional): Some officers may also check for Vertical Gaze Nystagmus by raising the stimulus upward and holding it for at least 4 seconds. This is an additional indicator, often suggesting high doses of alcohol or certain drugs, but it is not scored as part of the standard HGN clues.
Clues for Impairment (Maximum 6; 4+ Clues Typically Suggest Impairment):
| Clue | Description |
|---|---|
| Lack of Smooth Pursuit (2 clues, 1 per eye) | Your eyes jerk instead of following the stimulus smoothly. |
| Distinct and Sustained Nystagmus at Maximum Deviation (2 clues, 1 per eye) | Clear, ongoing jerking when your eyes are held at the farthest side point. |
| Onset of Nystagmus Prior to 45 Degrees (2 clues, 1 per eye) | Jerking begins before your eyes reach approximately 45 degrees from the center. |
| Vertical Gaze Nystagmus (additional indicator, not scored) | Upward jerking when your eyes are elevated fully; often indicates significant impairment. |
2. Walk-and-Turn (WAT)
This is a divided-attention test that assesses your balance, coordination, and ability to follow multi-step instructions while performing a physical task.
Administration Procedures:
- Setup: The officer will use a straight line (either a visible line on the ground or an imaginary one) on a flat, dry, non-slippery surface.
- Initial Stance & Instructions: You will be instructed and demonstrated: “Place your left foot on the line, and then place your right foot directly in front of it, heel-to-toe. Keep your arms at your sides. Do not start until I tell you to.”
- Full Instructions: The officer will then provide the full instructions: “When I tell you to begin, take nine heel-to-toe steps forward along the line. When you reach your ninth step, turn around by keeping your front foot on the line and taking several small steps with your other foot to turn around. Then, take nine heel-to-toe steps back along the line. While walking, keep watching your feet, count your steps aloud, and keep your arms down at your sides. Do not stop once you start.”
- Confirmation & Start: The officer will ask if you understand and then say “begin.”
- Important Notes: The officer should offer you the option to remove high-heeled shoes (heels greater than 2 inches). Any physical limitations you mention should be documented.
Clues for Impairment (Maximum 8; 2+ Clues Typically Suggest Impairment):
| Clue | Description |
|---|---|
| Cannot keep balance during instructions | You lose your heel-to-toe stance while the instructions are being given. |
| Starts too soon | You begin walking before the officer says “begin.” |
| Stops while walking | You pause during the walk for no apparent reason. |
| Misses heel-to-toe | A gap of greater than ½ inch occurs between your heel and toe on any step. |
| Steps off line | Your foot leaves the designated line. |
| Uses arms to balance | You raise your arms more than 6 inches from your sides to maintain balance. |
| Improper turn | You turn incorrectly (e.g., pivot instead of taking small steps as instructed). |
| Incorrect number of steps | You take a number of steps other than nine in either direction. |
3. One-Leg Stand (OLS)
This test further evaluates your balance and time estimation abilities under divided attention.
Administration Procedures:
- Initial Stance & Instructions: You will be instructed and demonstrated: “Stand with your feet together and your arms at your sides. Do not start until I tell you to.”
- Full Instructions: The officer will then provide full instructions: “When I tell you to begin, raise one leg of your choice about six inches off the ground, keeping your raised foot parallel to the ground and your leg straight. Look at your raised foot and count aloud, starting with ‘one thousand one, one thousand two,’ and so on, until I tell you to stop.”
- Timing: The officer will typically time you for 30 seconds internally.
- Confirmation & Start: The officer will ask if you understand and then say “begin.”
- Important Notes: The officer may test both legs if necessary, and any footwear or physical limitations should be documented.
Clues for Impairment (Maximum 4; 2+ clues typically suggest impairment):
| Clue | Description |
|---|---|
| Sways while balancing | Your body moves significantly side-to-side or back-and-forth. |
| Uses arms to balance | You raise your arms more than 6 inches from your sides to maintain balance. |
| Hopping | You use hops on your stationary foot to maintain balance. |
| Puts foot down | You lower your raised foot before the 30 seconds are up (each instance can be noted, but typically counts as one clue). |
If conditions prevent safe administration (e.g., strong wind, extremely uneven ground, heavy traffic), officers may decide to skip the Walk-and-Turn or One-Leg Stand and rely solely on the HGN test or other evidence of impairment. It’s vital to remember that these tests are not infallible and can be affected by factors unrelated to alcohol or drug impairment, such as medical conditions, extreme fatigue, or even simple nervousness.
Can Standardized Field Sobriety Tests Be Challenged? Absolutely.
While SFSTs are designed to be reliable tools for law enforcement, their results are frequently challenged in court. A skilled DWI defense attorney understands that these tests, despite being “standardized,” are often administered imperfectly or interpreted subjectively. Challenging the SFSTs can be a critical component of your defense strategy, potentially leading to a dismissal or reduction of charges.
Here are the primary grounds upon which SFST results can be challenged:
- Improper Administration by the Officer: This is the most common and often strongest basis for a challenge. Officers are required to follow NHTSA’s precise, step-by-step instructions. Any deviation can compromise the test’s validity.
- Incorrect Instructions: Did the officer clearly give all instructions and demonstrations? Did they ask if you understood before starting?
- Improper Scoring: Did the officer correctly identify and score the clues according to NHTSA guidelines? Are they counting non-standard “clues”?
- Failure to Document Deviations: Did the officer fail to note external factors (e.g., wind, uneven ground, passing vehicles, poor lighting) or your physical condition (e.g., age, injury, footwear) that could influence performance?
- Inexperience/Inadequate Training: While less common, an officer’s training records could be reviewed to ensure they are certified in SFST administration.
- Subject Conditions Unrelated to Impairment: Many factors can affect your performance on SFSTs that have nothing to do with alcohol or drug consumption.
- Medical Conditions: Inner ear problems, neurological disorders, leg or foot injuries, back problems, vertigo, nystagmus (pre-existing eye jerking), diabetes, or certain medications can mimic impairment clues.
- Age and Weight: Individuals over 65 or significantly overweight may struggle with balance and coordination tests even when sober.
- Fatigue or Stress: Extreme tiredness, anxiety, or nervousness can impair focus and physical performance.
- Footwear: High heels, platform shoes, or even flip-flops can make balance tests difficult.
- Inherent Physical Limitations: Some individuals simply have poor coordination or balance naturally.
- Environmental Factors: The conditions at the scene play a significant role.
- Surface: Was the ground uneven, sloped, gravelly, wet, icy, or littered with debris?
- Lighting: Was it too dark for you to see the line or your feet clearly? Was there blinding oncoming traffic?
- Weather: Strong winds, rain, or extreme cold can make performing these tests difficult and affect balance.
- Distractions: Passing traffic, sirens, or a noisy environment can disrupt your focus and divided attention.
- Subjectivity of Officer Observation: While the tests are standardized, the officer’s observation and interpretation of your performance can be subjective. Video evidence, if available, becomes crucial here to verify the officer’s claims against your actual performance. Without a recording, it often becomes a “he said, she said” scenario.
The Critical Role of Legal Counsel: JC Law
If you are facing a DWI charge, the ability to challenge the effectiveness and proper administration of SFSTs is paramount. This is where the expertise of experienced lawyers at JC Law becomes invaluable. A skilled DWI defense attorney will meticulously review every aspect of your case, including:
- Police Reports and Affidavits: They will scrutinize the officer’s narrative for inconsistencies, omissions, or misinterpretations of your SFST performance.
- Dashcam and Bodycam Footage: Video evidence is often the strongest tool for challenging SFSTs. Your attorney will analyze the footage frame-by-frame to determine if the officer followed proper procedure, if your performance was accurately reflected, and if environmental or physical factors were at play.
- Officer Training Records: In some cases, your attorney may investigate the arresting officer’s training and certification in SFST administration.
- Consulting Experts: Depending on the specifics of your case, they might consult with medical experts or accident reconstructionists to explain how non-impairment factors could have influenced your test results.
By identifying and highlighting errors in administration, subjective interpretations, or the influence of external factors, your attorney can argue to suppress the SFST evidence or significantly weaken the prosecution’s case. This can lead to reduced charges, a favorable plea bargain, or even a complete dismissal.
In conclusion, while the Standardized Field Sobriety Tests are a widely used and important tool for law enforcement in DWI investigations, they are not without their limitations. Understanding how these tests are administered and, crucially, how their results can be challenged, empowers you to protect your rights. If you find yourself subjected to SFSTs, remember that consulting with knowledgeable legal counsel, like lawyers at JC Law, is your best course of action to navigate the complexities of DWI law and build a strong defense.