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Are DUI Blood Tests Always Accurate?

 Posted on November 11, 2022 in DUI

Wheaton DUI defense lawyerJust as in the vast majority of the United States, the legal limit for blood alcohol concentration (BAC) in Illinois is 0.08 percent. If someone has a BAC of 0.08 percent or greater, they are considered to be intoxicated. Blood alcohol testing is usually a crucial component in a drunk driving case. The prosecution will have a very hard time securing a conviction for driving under the influence (DUI) without a blood test. 

However, alcohol blood tests are not always as reliable as you might think. Human error, product defects, and other problems can cause inaccurate results. If you or a loved one are facing DUI charges, it is important to know how blood alcohol test results may influence the case.  

Problems with Blood Testing in a DUI Case 

Someone accused of drunk driving may be required to undergo a blood draw for the purpose of BAC testing. The person’s blood is analyzed in a laboratory and tested for alcohol and other substances. Blood tests may be inadmissible during a DUI case due to:

  • Lack of probable cause – The prosecution must be able to show that there was probable cause for the blood draw. In the U.S. we have a Constitutional right against unjustified search and seizure. 
  • Chain of custody issues – the prosecution must have properly documented who drew the blood sample, the date and time of the blood draw, and the chain of custody for the sample. Any missing information or mistakes could be used to invalidate the blood test results. 
  • Inaccurate procedures – To test someone’s blood for alcohol or other substances, certain chemicals, including preservatives and anti-coagulants, are added to the blood sample. Adding too much or too little can ruin the test.  
  • Incorrect storage – Blood is a biological compound that will break down and decay over time. When a blood sample is not properly sealed and stored, it can become contaminated. The sample can even ferment, increasing the amount of alcohol in the sample and leading to false positives. 

Contact Our DuPage County DUI Defense Lawyers 

Blood tests are often an essential component of the prosecution’s case against an alleged drunk driver. However, there are many reasons that a blood test can be challenged. 

If you or a loved one were charged with driving under the influence, contact our Wheaton DUI defense lawyers for legal help. Our experienced team can evaluate the evidence against you and find any problems or weaknesses that may lead to an acquittal or even dismissal. Call Davi Law Group, LLC at 630-580-6373 for a free consultation. 



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