Three Phases Of A DUI Investigation

There are three phases to a DUI investigation that police are taught during the 24 hour National Highway Safety Administration (NHTSA) DUI Detection and Standardized Field Sobriety Tests course. Each phase is designed to accumulate evidence to ultimately establish probable cause to arrest for DUI.

Robert Hanaford of the Law Offices of Robert H. Hanaford is an experienced McHenry County DUI attorney who represents clients in the Chicago area and McHenry County, Illinois.

Robert has received his National Highway Safety Administration (NHTSA) instructor certificate to teach the 24 NHTSA police DUI Detection & Standardized Field Sobriety Tests course.

If you have been charged with a DUI and looking for an experienced DUI attorney in McHenry County or Chicago, call the Law Offices of Robert H. Hanaford at 24/7 on Robert’s cell phone at 312-636-4807.

The following is a discussion of the three phases of a DUI investigation.

PHASE ONE is Vehicle in Motion. The police officer needs reasonable suspicion to stop a vehicle. Somehow the officer’s attention is drawn to the vehicle, perhaps because of a citizen 911call or observing a traffic violation. The officer now decides whether to follow the vehicle and or stop the vehicle. Often the officer will follow the vehicle to obtain initial evidence of impaired driving. Interestingly, speeding is NOT indicative of impaired driving. However, driving too slow is a clue that the driver may be impaired. Other clues include disobeying traffic control devices, swerving within the lane of travel, swerving over the center line or edge line, delayed response to a traffic control device (such as staying stopped when a light turns green or slamming on the brakes for a stop sign or red light), stopping before or after the stop line, hitting the curb or entering the oncoming traffic lane during a turn.

The officer then must decide to pull the vehicle over or not. If the decision to stop is decided, the officer will observe the response time for the driver to recognize the squad car lights and pull over and how the driver pulls over. A driver that continues to drive oblivious to the flashing lights and then pulls over hitting the curb is providing evidence toward probable cause of DUI.

PHASE TWO is Personal Contact. It is here that the police officer first confronts the driver and is taught to use all senses to determine whether the driver may be DUI: Sight, smell and hearing.

The officer is looking for how the driver appears and responds to questions and whether there is the smell of alcoholic beverage. The officer will employ what is known as divided attention tactics by asking for the driver’s license, registration and proof of insurance. He will then often interject with a question such as where are you coming from and where are you going, all the while observing the driver’s coordination in retrieving the requested documents and how the driver responds to the questions. Are the answers coherent? Is the driver fumbling around for his license? Does the driver have slurred speech and glassy eyes? Does the driver admit to drinking and state an amount? Everything going on at this point is to compile evidence of probable cause to arrest for DUI and ultimately to establish guilt beyond a reasonable doubt.

The decision at this point is whether to request the driver to exit the vehicle to administer the field sobriety tests that are discussed in another article.

PHASE THREE is Pre-Arrest Screening. The officer requests that the driver exit the vehicle. You are not required to exit the vehicle unless the officer decides to arrest you. However, once the officer decides to have the driver exit the vehicle he has likely made up his mind that he will arrest the driver for DUI. The officer will observe how the driver exits the vehicle. Does he have difficulty getting out of the vehicle? Does he lean and hang on to the vehicle for balance? Does he have difficulty walking and standing.

Next the officer will administer the field sobriety tests. Again, by this point the officer is usually just accumulating more evidence of probable cause for a DUI arrest and to help the prosecutor establish proof of DUI beyond a reasonable doubt.

Finally, the decision to arrest or not is made. If arrested, the driver will be hand cuffed, placed in the police car and transported to the police station where he will be asked to take a breathalyzer test.


Note that a driver is only required to produce their license, registration and proof of insurance. The driver is not required to answer any questions and is not required to exit the vehicle or take field sobriety tests. In fact, a driver could only roll the window down enough to hand through the requested documents avoiding the smell of alcoholic Beveridge from being smelled. The officer must then decide whether he has enough evidence for probable cause to arrest. At that point, the driver would be required to exit the vehicle. In addition, the refusal to take the field sobriety tests would be admissible at trial as a presumption of impairment.

For further questions and a free consultation, call Robert H. Hanaford - DUI lawyer in McHenry County, Chicago at 312-636-4807.