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Blood/Breath Tests

Many people who submit to a chemical test (blood, breath or urine) and register above the legal limit (.08% blood alcohol for DUI and .02% blood alcohol for Underage DWI) often believe that their case cannot be successfully defended and choose not to retain a lawyer. An investigation of the case by a Tennessee DUI attorney, however, often reveals evidence that calls into doubt the reliability of the chemical test and may even result in keeping the test results from being introduced in court.

The Tennessee DUI lawyer you hire should be familiar with the many factors which can affect the result of a chemical test (blood test, breath test or urine test). Such factors often lead to an incorrectly high blood alcohol concentration. Depending on the type of specimen and analysis, the following are some of the factors that should be investigated to ensure the reported chemical test was accurate:

  • Radio Frequency Interference (which may be caused by a police radio, a microwave or a cellular telephone)
  • Mouth Alcohol during collection of a breath sample
  • Foreign substances in the mouth (for example, tongue stud or dentures)
  • Gastroesophageal Reflux Disease (GERD)
  • Diabetes
  • Method of blood extraction
  • Blood sample storage
  • Preservation of the blood sample
  • Transportation of the blood sample
  • Blood or breath sample analysis
  • Proper elimination of the breath sample from the body

The blood test

Was the blood drawn within the time specified by law? Was the blood drawn by a person that is certified? Was the proper amount and type of preservative used in the vial used to store the blood? Was the blood properly stored after the test? Is there a sample readily available for the defense to test independently? Are the officials, procedures and equipment used in the test all certified by the proper authorities?

The breath test

When was the breath machine last calibrated? Has the machine been serviced just before or after the test? Has the equipment and the operator been certified by the state? Exactly what calculations does the device use in order to convert air flow alcohol to blood alcohol? Is the device susceptible to outside interference coming from nearby electronic equipment? Did the individual burp or belch just before taking the test? Did the individual use mouthwash or breath spray that may have contained alcohol before taking the test?