Other than field sobriety tests, Illinois police officers will often use a breath testing machine that is designed to measure your blood alcohol content (BAC). If the machine indicates that your BAC is .08 or higher, you will more than likely be arrested on suspicion of drunk driving. This could make you wonder whether you should even agree to do the breath test.
When you obtained a driver's license, you agreed to submit to a breath test if an officer suspects you of driving under the influence during a traffic stop. Because of Illinois' implied consent law, refusing to take a breath test means that your driver's license is automatically suspended. Even so, some people might think that they would be better off not submitting to the test.
The real issue with breath tests is that they are not necessarily reliable. The machines need to be calibrated periodically. If they are not properly maintained, the results of your breath test could be skewed. In the alternative, the officer could make a mistake. If an investigation into the machine and the officer indicate that either of these issues occurred, the judge could throw out the results of the test.
Since the breath test was more than likely part of the reason that you were arrested for drunk driving, the charges against you could begin to fall apart without those results. Prosecutors need to be able to prove your guilt beyond a reasonable doubt in a court of law. Without the breath test, that might not be possible, and the charges could be dismissed.