There are two main chemical tests used to determine a person’s blood alcohol content (BAC). The first is a breath test, often called a breathalyzer, that determines blood alcohol based on the amount of alcohol on the test taker’s breath. The second is a blood test that directly determines the amount of alcohol in the subject’s blood. However, these tests are not infallible. False positives and inaccurate results can be caused by human error, improper storage, defective devices, and several other issues. If you or a loved one are facing charges for driving under the influence (DUI), do not lose hope. You or your loved one may still be able to avoid conviction by discrediting the results of chemical BAC tests.
Understanding the Limits of Breath Alcohol Tests
If you have even been pulled over on suspicion of drunk driving, you are probably familiar with the portable breathalyzer tests carried by police officers. These preliminary tests are used to create probable cause for a DUI arrest. However, the results of the preliminary breathalyzer are not admissible as evidence against the defendant in DUI proceedings. Typically, once an alleged drunk driver is taken to the police station, he or she is required to complete a second breath test on a device with greater accuracy. The results of this evidentiary breath test may be used as evidence in court. However, both evidentiary tests and preliminary tests can be unreliable.
Breathalyzers must be regularly calibrated and cleaned to yield accurate results. Improper test administration, conducting the test at the wrong time, and defects with the testing device may also lead to inaccurate results.
Blood Alcohol Tests and DUI Charges in Illinois
Another way police may determine an alleged drunk driver’s BAC is through a blood test. Blood is drawn from the subject and analyzed to determine the amount of alcohol per unit of blood. However, blood alcohol tests may be faulty. There are several steps involved in blood testing. The technician must mix certain chemicals such as anticoagulants and preservatives into the sample. These chemicals must not be expired or mixed incorrectly. The blood sample must be properly identified and stored. The sample must also be free of contaminants like ethyl alcohol from an alcohol swab. Mistakes during the blood draw, blood sample storage, or analysis of the sample can discredit the blood test results making it much more difficult for the prosecution to prove that a driver was under the influence....