How Can Field Sobriety Tests Lead to DUI Conviction?

Illinois DUI defense attorneys explaining how field sobriety test results are used to convict drivers.

Mike McMahon

July 5, 2025

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How Can Field Sobriety Tests Lead to DUI Conviction?

Field sobriety tests can lead to DUI conviction in Illinois because police use your test results as proof you were too drunk to drive safely. Even if you refuse the breath test, police can still arrest you and charge you with DUI based only on how you did on roadside tests like walking in a line or standing on one leg.

Many sober people fail these tests because they're hard to do, but judges and juries often think failing the tests means you were drunk, making conviction much more likely.

Common Field Sobriety Tests Police Use

Police in Illinois use three main roadside tests that were made by the government to check if drivers are drunk.

Walking in a line test:

You must walk 9 steps heel-to-toe in a straight line, turn around a certain way, and walk back
Police watch for 8 specific mistakes like stepping off the line, using arms for balance, or taking the wrong number of steps
Making 2 or more mistakes means police think you're drunk
Even sober people fail this test about 32% of the time in perfect conditions

Standing on one leg test:

You must stand on one foot for 30 seconds while counting out loud and keeping your arms at your sides
Police look for 4 signs of being drunk like swaying, using arms for balance, hopping, or putting your foot down
Showing any of these signs means police think you're too drunk to drive
Sober people fail this test about 17% of the time under perfect conditions

Eye tracking test:

Police use a pen or finger to check how your eyes move when following an object
They look for jerky eye movements that can happen when people drink alcohol
This test has problems because many things besides alcohol cause jerky eye movements
Police often do this test wrong because they don't have enough training

How Field Sobriety Tests Lead to DUI Conviction

Police use field sobriety test results as the main proof in DUI cases where there's no breath test or blood test.

How tests become evidence:

Police write reports about how you did on each test and what mistakes you made
Video recordings from police cars or body cameras show your test performance
Police testify in court about what they saw and why they think you were drunk
Judges and juries often believe that failing roadside tests means you were too drunk to drive

Why test results are powerful evidence:

People think the tests work perfectly and don't know sober people often fail them
Police present themselves as experts who know how to spot drunk drivers
Videos can look bad even when you're actually sober but nervous or scared
Most people don't fight the test results because they don't know they can challenge them

How failing tests hurts your case:

Creates probable cause for police to arrest you for DUI
Gives police reason to take you to the station for breath or blood tests
Becomes main evidence if breath test results can't be used in court
Makes plea bargains harder because police think they have strong evidence against you

Problems with Field Sobriety Tests

Field sobriety tests have many problems that make them unreliable ways to tell if someone is drunk.

Test conditions affect results:

Uneven ground makes balance tests much harder even for sober people
Bad weather like rain, wind, or cold makes tests nearly impossible to pass
Poor lighting at night makes it hard to see where you're supposed to walk
Traffic noise and flashing police lights make it hard to focus and follow directions

Physical problems that cause test failure:

Age over 65 makes balance tests much harder to pass
Being overweight affects your ability to balance on one foot
Injuries or medical problems with your back, legs, or inner ear cause balance issues
Wrong shoes like high heels or worn-out soles make walking tests dangerous

Police training problems:

Many officers don't get enough training on how to give tests correctly
Officers often skip steps or change the test instructions
Police don't account for medical problems or physical conditions that affect test results
Officers may have bias and look for signs of being drunk even in sober people

How to Defend Against Field Sobriety Test Evidence

You can fight field sobriety test results in court by showing the tests are unreliable or were done wrong.

Common defense strategies:

Medical conditions that explain why you couldn't do the tests right
Bad test conditions like poor lighting, uneven ground, or bad weather
Police mistakes in giving the tests or not following proper steps
Physical problems like injuries, age, or weight that affect balance and coordination
Nervousness and fear from being pulled over that affected your ability to focus

Challenging test procedures:

Video evidence often shows police didn't follow correct test procedures
Police training records may show the officer wasn't properly trained
Test conditions can be shown to be unfair or dangerous
Alternative explanations for poor test performance that don't involve alcohol

Common Questions About Field Sobriety Tests and DUI

Do I have to take field sobriety tests?

No, you can refuse roadside tests in Illinois without losing your license, but police may still arrest you based on other things they see.

Can I be convicted with only field sobriety test results?

Yes, police can get DUI convictions using only roadside test results if they convince a judge or jury the tests prove you were drunk.

Are field sobriety tests accurate?

No, even the government studies show sober people fail these tests 17-32% of the time under perfect conditions, and real roadside conditions are never perfect.

What if I have medical problems?

Medical conditions like diabetes, inner ear problems, or back injuries can make it impossible to pass field sobriety tests even when you're completely sober.

Can police force me to take the tests?

No, police cannot physically force you to take roadside tests, but they may use your refusal as one factor in deciding to arrest you.

Many people don't know they can challenge field sobriety test results in court. These tests have serious problems that make them unreliable proof of being drunk.

For complete information about defending against field sobriety test evidence, see our DuPage County Under the Influence DUI defense guide.