Types of Field Sobriety Tests

When a police officer suspects a driver of drunk driving, they may conduct field sobriety testing to check for signs of impairment. These tests help determine if a driver has a blood alcohol concentration (BAC) over the legal limit, but they are not always accurate. Many factors, such as physical ailments, anxiety, or environmental conditions, can lead to false indicators of intoxication that may not actually reflect alcohol use.

In Naperville, Illinois, it’s important to understand how these tests work, how officers interpret signs of impairment, and what your rights are under consent laws. Even if you haven’t exceeded the blood alcohol level, failing a field sobriety test could still result in a DUI charge. Understanding these tests can help you make informed decisions if you are ever asked to perform one. An experienced DUI defense attorney in Naperville can scrutinize the administration of these tests and challenge their validity in court.

If you've been charged with a DUI in Illinois, call our law firm today at (630) 425-0250 to discuss your case and explore your legal options.

What Are the Standardized Field Sobriety Tests (SFSTs)?

The Standardized Field Sobriety Tests (SFSTs) were developed by the National Highway Traffic Safety Administration (NHTSA) to help officers identify indicators of intoxication. These tests are considered more reliable than non-standardized methods, but they still rely on officer interpretation and are subject to errors due to outside factors.

There are three main standardized tests used during field sobriety testing:

Horizontal Gaze Nystagmus (HGN) Test

The Horizontal Gaze Nystagmus (HGN) test is one of the most commonly used tests to check for indicators of intoxication. It measures involuntary jerking of the eyes, which can become more pronounced when a person is under the influence of drugs or alcohol.

During this test:

• The police officer holds an object, such as a pen or flashlight, and asks the suspect to follow it with their eyes.
• The officer looks for smooth pursuit movement and checks whether involuntary jerking occurs.
• The presence of natural nystagmus (a condition where a person’s eyes naturally move slightly) is considered, but law enforcement officers mainly focus on the onset of nystagmus at lesser angles or peripheral angles. If eye jerking begins before the eye moves to a 45-degree angle, it may indicate alcohol impairment.

Factors that can affect results:

• Some physical ailments, neurological disorders, or eye conditions can cause natural nystagmus, leading to false indicators of intoxication.
• Flashing police lights, bright headlights, or environmental distractions can make it difficult for a suspect to follow the object smoothly.

Walk-and-Turn Test

The Walk-and-Turn test measures a person’s balance, coordination, and ability to follow instructions. This test is divided into two phases: the instruction phase and the walking phase.

During this test:

• The suspect must take nine heel-to-toe steps in a straight line, turn on one foot, and walk back in the same manner.
• Officers look for signs of impairment, such as stepping off the line, failing to turn properly, or using arms for balance.

Factors that can affect results:

• Uneven road surfaces, gravel, or slippery conditions can cause a person to lose balance, even if their blood alcohol concentration is below the legal limit.
• Certain physical ailments, such as back pain or leg injuries, can affect a person’s ability to walk in a straight line.

One-Leg Stand Test

The One-Leg Stand test is another common method used to determine signs of impairment.

During this test:

• The suspect must stand on one leg while counting out loud until instructed to stop.
• The officer observes whether the person sways, hops, or puts their foot down prematurely, all of which are considered indicators of intoxication.

Factors that can affect results:

• A suspect’s level of impairment may not be the only factor affecting balance—medical conditions, fatigue, or even cold weather can contribute to difficulty completing the test.
• Poor footing, road slopes, and environmental distractions can impact performance.

Non-Standardized Field Sobriety Tests

In addition to SFSTs, some police officers use non-standardized field sobriety tests to assess signs of intoxication. These tests are not validated by the NHTSA, meaning they can vary between officers and departments.

• Finger-to-Nose Test – The suspect closes their eyes and touches their nose with their index finger, testing coordination and depth perception. Physical ailments such as joint pain or muscle stiffness can impact results.
• Reciting the Alphabet or Counting Backwards – Officers may ask a suspect to recite the alphabet or count backwards to test cognitive function. However, anxiety or language barriers can make this test unreliable.
• Rhomberg Balance Test – The suspect tilts their head back, closes their eyes, and estimates 30 seconds. Officers look for excessive swaying, poor timing, or difficulty maintaining balance as indicators of intoxication.

Because these tests are not standardized, their accuracy depends heavily on the police officer’s interpretation.

Accuracy of Field Sobriety Tests and Defenses Against Them

While field sobriety testing is meant to detect impaired driving, many outside factors can lead to unreliable results:

• Medical Conditions or Physical Impairment – Inner ear problems, physical ailments, or neurological disorders can cause balance issues unrelated to blood alcohol content.
• Weather and Road Conditions – Slippery pavement, wind, or uneven ground can make it difficult to perform certain tests.
• Nervousness or Fatigue – Anxiety and exhaustion can affect coordination, causing indicators of impairment even in sober individuals.

Criminal defense attorneys often challenge field sobriety testing by:

• Questioning whether the police officer administered the test correctly.
• Presenting medical records to explain balance or coordination difficulties.
• Highlighting environmental factors that could have influenced the suspect’s ability to perform the test.

Since these tests are subjective, they should not be the sole basis for a DUI charge.

Can I Refuse to Take a Field Sobriety Test in Illinois?

Yes, you can refuse to take a field sobriety test in Illinois, and doing so does not carry automatic penalties. Unlike chemical tests, field sobriety tests are not covered under Illinois’ implied consent law, which applies only to breath, blood, and urine tests.

• No Automatic License Suspension: Since field sobriety tests are voluntary, refusing them will not trigger an immediate suspension like refusing a breath or blood test would.
• Subjective and Unreliable: These tests rely on an officer’s judgment, and factors like medical conditions, anxiety, or uneven surfaces can lead to inaccurate results.
• Possible Impact on Your Case: While refusal cannot be used as direct proof of intoxication, an officer may still arrest you based on other observations, such as slurred speech, alcohol odor, or poor driving behavior.

If you are pulled over for suspicion of DUI, remaining calm, politely declining field sobriety tests, and requesting a lawyer can help protect your rights.

What Happens if You Fail a Field Sobriety Test in Illinois

If you fail a field sobriety test in Illinois, here's what typically happens:

• You may be arrested for DUI: Failing one or more field sobriety tests gives the officer probable cause to arrest you on suspicion of driving under the influence.
• You’ll likely be asked to take a chemical test: After arrest, you’ll be taken to the station and asked to take a breath, blood, or urine test. Refusing can lead to automatic license suspension, even if you weren’t drinking.
• Your license could be suspended: Failing the chemical test can trigger a statutory summary suspension of your driver’s license. This is separate from any criminal penalties and begins 46 days after your arrest.
• The test results may be used in court: The officer’s observations and your performance on the tests may be used as evidence against you in court. However, these tests can be challenged based on how they were administered or other factors (like medical conditions, fatigue, or uneven terrain).

Want to go into how field sobriety tests are challenged or what the penalties are after arrest?

Facing a DUI? Talk to a Lawyer Today

Field sobriety tests are commonly used in DUI investigations, but they are not always accurate. Criminal defense lawyers frequently challenge these tests due to their subjectivity and vulnerability to outside influences.

If you have been charged with a DUI in Naperville, Illinois, after taking or refusing a field sobriety test, a skilled DUI defense attorney can review your case, challenge the evidence of impairment, and work to protect your rights.

Contact Naperville DUI Lawyer today for a consultation and discuss your legal options.