DUI Testing

If a police officer has reasonable suspicion that you’re intoxicated, he or she may ask you to submit to a number of tests designed to determine whether you are either intoxicated or over the legal limit of .08 blood alcohol content (BAC). Some of these tests are given in the field, and others you may have to take when once you’re in police custody.

Contrary to what many think, drivers do not have the right to speak to an attorney before they are tested. These tests must be given as soon as possible after you are pulled over, so it will be up to you to decide whether it’s in your best interest to refuse or agree to take these tests. You may decline to take a roadside sobriety or preliminary breath test without consequence. But if you decline to give a blood, urine, or breath sample once you’re in police custody, you will face an automatic administrative license suspension.

If you drive on a public highway in Illinois, you give your consent to providing a blood, urine, or breath sample when an officer has probable cause to believe you are intoxicated. An officer may have probable cause to believe you are intoxicated when:

  • You were driving erratically
  • You failed a field sobriety test
  • You behaved strangely
  • You smelled like alcohol or weed
  • Your eyes were glassy or red

What Are Field Sobriety Tests?

The National Highway Traffic Safety Administration (NHTSA) has approved three field sobriety tests that police officers may use to gauge whether a suspect is intoxicated: the Horizontal gaze nystagmus test, the walk and turn test, and the one legged stand test.

The walk and turn and one-legged stand tests both place suspects in a position in which they must demonstrate that they have the same balance and coordination as a sober person. The horizontal gaze nystagmus is subtler. It involves the officer examining the suspect for signs of nystagmus, the involuntary jerking of the eyes often exhibited by people who have consumed alcohol or other intoxicating substances.

According to one study, these tests offered the following accuracy rates in predicting whether a subject’s BAC was at .10 or above:

  • Horizontal gaze nystagus—77% accuracy
  • Only walk and turn—68% accuracy
  • Only one legged stand—65% accuracy
  • Horizontal gaze and walk and turn—80% accuracy

The NTHSA provides detailed instructions for the proper administration of field sobriety tests. Indeed, its training manuals emphasize that the tests are accurate only when:

  • The tests are given in the correct, standardized way
  • Standardized cues are used to determine the suspect’s performance
  • The officer giving the tests follows standardized criteria in interpreting the suspect’s performance

What this means is that your DUI defense attorney can have the results of these tests excluded from the prosecutor’s case if he or she can have the police officer admit that the test was not administered strictly by the book. Additionally, your attorney can argue that you may have failed a field sobriety test because of:

  • Your age, weight, or an illness
  • Slippery road conditions
  • Inappropriate footwear
  • Disorientation from flashing lights if arrest occurred at night

What Is the Preliminary Breath Test?

Every police car patrolling the roads of Illinois contains a portable preliminary breath testing device. This device takes a sample of your breath and gives a reading of your BAC. If you blow over .08, the prosecutor can use this result as evidence of the officer’s reasonable cause to place you under DUI arrest and to make you take a more accurate chemical test at a medical facility.

The result of the preliminary breath test cannot be used to prove that your BAC was actually over the legal limit—it’s all about proving probable cause. Thus, it may be in your best interest to refuse a preliminary breath test. Just like with the field sobriety test, there are no consequences for refusing. You may still get arrested—if the officer smells alcohol on your breath and you exhibit signs of drunkenness, for example—but you’ll be giving the prosecutor less evidence to use against you.

If you are confident that you will blow under .08, you may want to take the preliminary test. If you pass the test, the police officer will lose his or her reason for detaining you and must let you go, unless he or she develops other suspicions from the encounter.

What Are the Chemical Blood or Urine Tests Given at a Medical Facility?

The blood or urine tests you must submit to after your DUI test will take place at a medical facility, where they must be administered by licensed medical professionals. You may choose to decline these tests, but if you do, you’ll face the automatic suspension of your license. If your DUI arrest arose out of an accident resulting in injury, you cannot refuse a chemical test, and the police can even use force to get a sample from you.

Your sample must be collected, labeled, and sealed in the presence of a law enforcement officer, who must authenticate it. Before conducting his or her analysis, the forensic scientist must photograph the sealed sample box with the arresting officer’s initials.

If your attorney can show that there was an irregularity in the chain of custody of the sample box, or that some lapse in procedure occurred, the prosecutor may not use your blood or urine sample as evidence of your intoxication. This is because the authorities must be able to show that no one altered or tampered with your samples between the time they were collected and when they were analyzed.

The blood test given on an emergency basis (after an accident involving an injury) is different than the normal blood test. These serum tests often show a higher BAC than regular blood tests, so the authorities must present a BAC result that is corrected by a factor of 1.18. The issue of converting serum test results to the scale of normal blood tests if a frequent issue in
Illinois DUI cases.

Failing a DUI Test Does Not Mean Your Case Is Lost

As explained above, there are many scenarios under which a skilled Chicago DUI charges lawyer can have evidence of your failed sobriety, breath, urine, or blood test rejected from the prosecutor’s case. The authorities must comply with precise and extensive regulations, and lapses occur frequently. Your attorney must study the prosecutor’s evidence closely and look for any loopholes.

As a former prosecutor with over 20 years of experience prosecuting and defending DUI cases, Chicago criminal defense lawyer Michael S. O’Meara has the experience necessary to find the flaws in the prosecutor’s case. If you’ve been charged with DUI, call O’Meara law today for a free and confidential consultation of your case at .