DUI Testing in Illinois: Field Sobriety Tests, Blood Tests, and Breathalyzers
Defense Attorney in Chicago, Illinois
If you are pulled over under suspicion of driving under the influence (DUI) in Illinois, law enforcement may require you to undergo DUI testing to determine your level of impairment. These tests include field sobriety tests, breathalyzer tests, and blood tests, all of which play a crucial role in DUI arrests in Illinois. However, not all tests are reliable, and officers don’t always follow proper procedures, which can lead to unjust DUI charges.
At Bernard Law, we understand how DUI testing works and how to challenge test results that may be inaccurate or unlawfully obtained. If you’ve been charged with DUI, understanding your rights and the limitations of these tests can make all the difference in your case.
Field Sobriety Tests in Illinois
One of the first drunk driving tests police officers may conduct is a field sobriety test (FST). These are physical and cognitive exercises designed to assess whether a driver is impaired by alcohol or drugs. However, these tests are highly subjective and prone to human error.
Common field sobriety tests include:
Horizontal Gaze Nystagmus (HGN) Test – The officer asks the driver to follow an object, such as a pen or flashlight, with their eyes while looking for involuntary jerking movements that may indicate intoxication.
Walk-and-Turn Test – The driver must walk heel-to-toe along a straight line, turn, and return in the same manner while following the officer’s instructions.
One-Leg Stand Test – The driver must balance on one leg while counting aloud.
While these tests are widely used, many factors can affect the results, including nervousness, medical conditions, uneven terrain, poor footwear, and even fatigue. In some cases, officers may also conduct a field sobriety test for drugs, looking for signs of impairment unrelated to alcohol. However, these tests are even less reliable, as they rely solely on an officer’s observations rather than scientific evidence. If you failed a field sobriety test and were arrested for DUI, our attorneys can challenge the accuracy of the test and determine whether law enforcement followed proper procedures.
DUI Breathalyzer Tests: What You Need to Know
A DUI breathalyzer test is one of the most common tools used by police to measure blood alcohol content (BAC). In Illinois, the legal BAC limit is 0.08% for drivers over 21, 0.04% for commercial drivers, and any detectable alcohol for drivers under 21 due to Illinois' Zero Tolerance Law.
There are two types of breath tests:
Preliminary Breath Test (PBT) – This is a handheld device used during a traffic stop to determine whether further testing is needed. However, PBT results are not admissible in court due to their inaccuracy and susceptibility to false readings.
Evidentiary Breathalyzer Test – If an officer determines there is probable cause for DUI, they may take the driver to a police station or testing facility to conduct an official breath test using a more accurate machine.
While breath tests are considered more reliable than field sobriety tests, errors in administration, improper calibration, and medical conditions can lead to false positives. Factors such as acid reflux, diabetes, residual alcohol from mouthwash, and improper officer training can all impact results.
Blood Test or Breathalyzer: Which One Is More Accurate?
A blood test or breathalyzer can both be used as evidence in a DUI arrest in Illinois, but they differ in accuracy and legal implications.
Blood Tests – A blood test is generally more accurate than a DUI breathalyzer test since it directly measures BAC. However, errors in collection, storage, and analysis can compromise results. Blood tests require proper chain of custody, and any break in protocol may render the test inadmissible in court.
Breathalyzer Tests – While commonly used, breathalyzer tests are prone to errors. If the device is not calibrated correctly or the officer administering the test lacks proper training, the results may be challenged.
You have the right to refuse a breathalyzer or blood test, but doing so carries penalties under Illinois’ Implied Consent Law. A refusal automatically results in a license suspension—one year for a first refusal and three years for a second refusal within five years. However, a refusal may also prevent the state from obtaining key evidence against you.
If you were given a test for drunk drivers and believe the results were inaccurate or mishandled, our legal team can investigate whether the test was conducted lawfully and challenge any unreliable evidence.
Can You Refuse a DUI Test in Illinois?
You do have the right to refuse field sobriety tests and preliminary breath tests (PBTs) without automatic penalties. However, refusing a breathalyzer or blood test after an arrest triggers penalties under Illinois’ Implied Consent Law, including:
1-year license suspension for a first-time refusal.
3-year license suspension for a second refusal within five years.
Refusing a test does not guarantee you won’t be charged with DUI—the prosecution can use other evidence, such as officer observations, video footage, and witness testimony. However, without a breath or blood test, it may be harder for prosecutors to prove intoxication beyond a reasonable doubt. Our DUI attorneys can evaluate whether refusing a test was in your best interest and work to minimize the consequences of a refusal.
Challenging DUI Testing in Illinois
DUI tests are not foolproof, and there are several legal strategies that can be used to challenge test results, including:
Improper Testing Procedures – If officers failed to follow correct procedures, the results could be invalid.
Faulty Breathalyzer Calibration – Breathalyzers must be regularly maintained and calibrated. Improper maintenance can lead to inaccurate readings.
Medical Conditions Affecting Results – Acid reflux, diabetes, or even a low-carb diet can cause false positives on a breath test.
Chain of Custody Issues with Blood Tests – If a blood sample was mishandled or improperly stored, the results may be inadmissible.
Lack of Probable Cause for the Stop – If the officer had no valid reason to pull you over, all evidence obtained after the stop may be suppressed.
If you were arrested for DUI in Illinois based on a DUI test, our skilled DUI attorneys can challenge the accuracy of the test results and protect your rights.
Contact Our DUI Defense Attorneys Today
If you are facing DUI charges in Illinois, don’t let a failed field sobriety test, DUI breathalyzer test, or blood test determine your future. At Bernard Law, we are well-versed in challenging DUI evidence, questioning the legality of testing procedures, and fighting to reduce or dismiss charges. DUI convictions come with severe penalties, including license suspension, heavy fines, and possible jail time. The sooner you contact an experienced DUI defense attorney, the better your chances of building a strong defense. Call Bernard Law today for a free consultation and let us fight for your rights.
