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What the Police Look for in an Illinois DUI Arrest

In Illinois as elsewhere, you cannot be arrested for DUI unless the police have probable cause. Probable cause refers to reasonable grounds to make an arrest. The police will look for various signs and perform different tests to acquire enough probable cause. In fact, the National Highway Traffic Safety Administration (NHTSA) has outlined specific criteria that would indicate probable cause for impairment.

At Dolci & Weiland, we believe that informed clients make the best decisions. Here, we outline below NHTSA's criteria as well as other factors that the police look for to obtain sufficient reasonable grounds for a DUI arrest in Chicago and DuPage County. Contact our office if you have been arrested and have additional unanswered questions or want to start your DUI defense today.

Reasonable Suspicion Prior to a Traffic Stop in Illinois

The police wait impatiently in their vehicles watching cars pass by well into the early morning hours. They are looking for moving violations that suggest drunk driving. These moving violations are sufficient reasonable suspicion to pull a motorist over for a traffic stop, and from the traffic stop -- depending on the circumstances -- the police can commence a DUI investigation.

There are many traffic violations that could indicate driving under the influence, but the most common are:

  • Weaving
  • Drifting
  • Swerving
  • Straddling a line
  • Driving on the wrong on a one-way street
  • Failing to use headlights at night 
  • Failing to maintain consistent speed
  • Making improper turns --  for example, turning too fast, too wide, or without a signal
  • Stopping too far from or too close to a traffic light, stop sign, or something similar
  • Driving too slow -- drivers often try to overcompensate for driving under the influence of drugs or alcohol by driving well under the speed limit
  • Braking at the sight of a patrol car.

The police report should state the reason why you were pulled over. An experienced DUI attorney knows to review a police report for this type of information. Without reasonable suspicion to pull you over, your constitutional rights may have been violated. At Dolci & Weiland, we will move the court to exclude any evidence flowing from the violation so that it cannot be used as evidence against you in an Illiniois DUI case.

The Illinois Traffic Stop: Signs & Tests

Once you are pulled over, the officer will make personal contact with you. While the officer asks his or her questions, he or she will also be observing you to determine whether or not you are impaired. Here are some of the symptoms and signs the officer will look for.


  • Bloodshot eyes
  • Glassy or watery eyes
  • Droopy eyelids
  • Dazed look
  • Blank staring
  • Twitching
  • Body tremors
  • Disheveled clothing


  • Argumentative
  • Aggressive
  • Obnoxious
  • Boisterous

Speech Indicators

  • Slurred speech
  • Loud speech
  • Rambling 
  • Fast or slow talking
  • Repetitive statements
  • Making irrational statement
  • Hesitant to not responding to questions

Behavioral Characteristics 

  • Staggering, swaying, or stumbling
  • Unable to sit straight
  • Careless or restless
  • Crying
  • Sudden change in behavior
  • Too animated
  • Unable to keep eye contact
  • Drowsy or falling asleep
  • Unable to remember
  • Disoriented 
  • Agitated or anxious

Other Indicators

  • Odors, like marijuana in the vehicle or alcohol on your breath
  • Excessive perspiration

As you can see, it's more the extreme physical and behavioral characteristics a person exhibits during a traffic stop that alerts a police officer to the possibility of intoxication. It is in your best interest to remain calm and polite. 

Keep in mind, too, the officer will scan your vehicle for any other signs that may be in plain sight. This could include things like open or empty containers, drug paraphernalia, or soiled clothing.

In any event, if the officer suspects drunk or drugged driving, you may be asked to conduct a test, like a preliminary breath test or field sobriety tests.

Roadside DUI Tests in Illinois

You may be asked to perform one of three standard field sobriety tests (FST) or to submit a breath sample for a preliminary breath test (PBT). None of the results from any of these tests are scientifically accurate and can be challenged at court -- in fact, PBTs are not admissible as evidence. These tests, however, are enough to provide an officer with probable cause to arrest you if you fail any one of these tests. 

The PBT is an instrument in which you must blow. If your breath alcohol content (BrAC) is at or above .08 percent, then you are legally intoxicated. The three field sobriety tests that you may be required to perform are:

  1. Horizontal gaze nystagmus (HGN) test. To perform this test, you must follow -- with your eyes -- the movement of the officer's finger or another instrument, like a pen, from side to side. The officer is generally looking for unusual eye movement to see if you can or not follow the moving object. 
  2. Walk and turn test. This is about coordination. The officer is again looking for specific things, like failing to follow instructions and losing balance, failing to walk toe to heel, stopping before told to do so, among several other indicators.
  3. One-leg stand test. This test is about coordination, too. The officer will ask you to balance on one leg for thirty seconds while he or she observes you for any swaying, putting the foot down, using the arms for balance, or hopping.

Remember, these tests won't likely be the deciding factor if you are convicted or not, but they can give a police officer enough reason to arrest you. Also know that you can refuse any of these tests, but there are risks. To refuse field sobriety tests, that alone could be used against you to indicate you were conscious of being illegally intoxicated. To refuse a breath test, that alone can result in suspension of your driver's license but for a longer period than the DUI arrest along would entail.

Who to Contact If You Have Been Charged with a DUI in Chicago IL

The police are looking for signs of illegal intoxication while driving. This will increase dramatically come 2020 when recreational marijuana is legal. You should be aware of your responses when pulled over and know that any extreme or otherwise bad behavior can get you arrested for a DUI. Contact Dolci & Weiland to learn more and to get started on a comprehensive, aggressive defense.