





July 7, 2020
DUI Defense Resources In order to be convicted of DUI in a court, the prosecutor must prove the charges beyond a reasonable doubt. Although this can be interpreted differently by judges, the job of the prosecution is to provide an abundance of evidence that makes it clear the driver was in fact unable to safely operate their moving vehicle and placed the lives of others at risk.
Here are some of the pieces of evidence used by the prosecution and how your Chicago DUI can dispute each one;
Table of Contents
ToggleThe arresting officer in your DUI case first became concerned about your ability to control your vehicle safely when they observed driving patterns that were indicative of someone who may be impaired. The officer began to follow your vehicle, record the actions on their dash camera, and eventually pulled over the vehicle after making the determination that there was something not quite right. The officer may have seen the vehicle hugging the center lane marker, driving much slower than the posted speed limit, it swerving and braking hard for no reason.
Although the prosecution will present this as part of their evidence in proving the driver was intoxicated, your DUI attorney can cast doubt on those driving concerns. When evidence is revealed the driver was suffering health issues or having an adverse reaction to medication, it could explain away the erratic driving patterns and part of the case for the prosecution.
The prosecution will utilize any correspondence between the officer and the driver in the evidence they present in court the driving was intoxicated. Once the officer has the driver safely pulled to the side of the road, they will question the driver about their behavior and try to determine if this was an isolated issue or if the driver is too impaired to safely control the vehicle. The conversation between the driver and the officer is recorded, and is crucial evidence used by the prosecution to show the state of mind and condition of the driver.
Although the video from the police dash camera does record the entire conversation, it could be difficult to get a clear indication of the physical state of the driver if they are only being judged by their words. The Chicago DUI attorney may present evidence that the driver was suffering from an illness at the time, but was not given the opportunity to explain themselves to the officer during the conversations they had.
When the officer feels there is just cause to test the driver for DUI, they have a number of field sobriety tests they can administer on the scene. The driver may be asked to take a breathalyzer, and then perform some physical tests while in plain view of the dash camera. The officer might ask the driver to stand on one leg with the other leg raised, recite the alphabet from T to Z backwards, or to walk a straight line in a very specific manner. The prosecution will use this evidence as part of their case to show that the driver was in no condition to be operating a vehicle.
The DUI attorney will try to discredit the evidence presented by explaining to the judge that the driver was afraid and nervous. When the judge shows the driver has no history of criminal activities and a clean driving record, they could try to discredit the test results by showing the driver was intimidated by the officer, afraid of being arrested, or simply did not clearly understand what the officer was requesting.
One of the strongest pieces of evidence that the prosecution will use to prove the driver was intoxicated is the blood alcohol test results. These tests are usually administered in the police station, are recorded, and are fairly accurate. The prosecution will use the reading to show beyond a reasonable doubt the driver was drinking and the numbers do not lie. Your DUI attorney knows that poking holes in this evidence will give the driver the best chance of winning the case.
A skilled DUI lawyer will begin by reviewing the tape and looking to see if the officer properly calibrated the testing equipment before the driver was tested. The attorney will look to see if that brand and model testing equipment has even been part of a recall or has given false readings in the past. One mistake here and the prosecution evidence could be removed from the case.
Although the prosecution only needs to prove the DUI charges against the driver by reasonable doubt, you want to put yourself in the best possible position to discredit the evidence by working with the best DUI attorney.
To convict a driver of DUI, the prosecutor must prove the charges beyond a reasonable doubt. This generally means presenting enough evidence to show the driver could not safely operate the vehicle and put others at risk.
The prosecution often uses evidence such as:
Driving pattern concerns observed by the officer
Questions and answers between the driver and officer
Field sobriety test results
Blood alcohol test results
Officers may become suspicious based on driving behaviors that appear impaired, such as:
Hugging the center lane marker
Driving far below the speed limit
Swerving
Braking hard for no reason
These behaviors may be recorded on dash camera and used by the prosecution.
Yes. A DUI attorney may cast doubt on the driving behavior by showing there may have been another explanation, such as:
Health issues
An adverse reaction to medication
This can weaken the prosecution’s argument that the driving patterns were caused by intoxication.
The prosecution may use the recorded conversation between the officer and the driver to show the driver’s condition, state of mind, and possible impairment. This correspondence can become key evidence in court.
Yes. Even if the dashcam records the conversation, it may still be difficult to judge the driver’s physical condition based only on words. A DUI attorney may argue the driver was sick or impaired by an illness and may not have had the opportunity to explain themselves fully.
The officer may use several field sobriety tests, such as:
Standing on one leg
Reciting the alphabet from T to Z backwards
Walking a straight line in a specific manner
Taking a breathalyzer test before or during testing
The prosecution may use the results to argue the driver was not fit to operate a vehicle.
A DUI attorney may challenge field sobriety tests by explaining the driver’s poor performance could be caused by:
Nervousness or fear
Being intimidated by the officer
Confusion about instructions
Lack of criminal history or a clean driving record supporting the argument that the driver was simply anxious
Blood alcohol test results are often considered one of the strongest pieces of evidence because they are typically administered at the police station, recorded, and generally viewed as accurate. Prosecutors often rely heavily on these results.
Yes. A skilled DUI attorney may look for errors such as:
Improper calibration of the testing equipment
Problems with the brand or model of equipment
Recalls or past false readings
Mistakes during testing procedure
If problems are found, the evidence may be weakened or possibly removed.
Because the prosecution must prove guilt beyond a reasonable doubt, challenging the credibility of key evidence can help create doubt and improve the driver’s chances of a better outcome.
An experienced DUI attorney understands how prosecutors build DUI cases and can identify weaknesses in evidence such as driving observations, test results, and police procedure. This gives the driver the best chance to discredit the prosecution’s case.
Montgomery 12/2016

