The fundamental piece of evidence in a DUI case is the driver’s blood alcohol level.  In order to find out a driver’s blood alcohol content, police have exceedingly begun using blood testing on scene.  In most cases, a driver must consent to such a test pursuant to A.R.S. § 28-1321 or risk a suspended license.  Although blood testing is generally more accurate than breath testing, there are still several possible errors that could occur during the process of ascertaining a driver’s blood alcohol level.  Since this form of testing is subject to error, it is important to consult an experienced Tucson criminal defense attorney to carefully evaluate each step in the blood testing process.

Blood Testing Results: Potential Mistakes

Below is a list of possible mistakes in a blood test result:

  1. Blood Draw:  The drawing of blood is a sensitive medical procedure, and the person drawing blood for the DUI investigation must be trained to do venipuncture/blood withdrawal.  Most officers performing this task on scene have limited background and training in the medical field.  As a result, a blood sample taken on site is more susceptible to contamination.
  2. Whole Blood or Plasma:  If the sample tested only comprised blood serum or plasma, there is a chance the results were inflated.  For a more accurate result, whole blood is recommended for testing.
  3. Hematrocrit: This is another variable unique to your body that could affect your blood alcohol level.  If you have a higher hematrocrit, which is the percentage of your blood made up of cellular material, you will show a higher blood alcohol content.  This is because your blood has a lower volume of liquid.
  4. Alcohol:  It is also possible for the rubbing alcohol used before and after the blood draw to contaminate the blood sample.
  5. Blood Test Kits:  These kits have expiration dates and should be checked prior to their use.  An expired kit could lead to a contaminated blood sample.
  6. Vacuum Tube: The vacuum tube is the part of the blood test kit that inures a precise amount of blood is drawn and mixed with preservative and anticoagulant.  If the tube was not functioning properly, contaminants such as yeast, alcohol, or microbes may have contaminated the sample.
  7. Blood Fermentation: It is possible for the blood to ferment inside the test kit before it is tested in a lab.  This can cause the blood to have a higher alcohol content than it should.
  8. Preservative:  The lab adds a chemical to pull the alcohol out of the blood and turn it into vapor.  This process is known as salting out and the higher the concentration of salting out agent, the higher the blood alcohol content.  If too much salting out chemical was used, the results could be inaccurate.
  9. Chain of Custody:  The chain of custody refers to the period between the time the police draw the blood to the time the sample is presented in court as evidence against the driver.  If there are significant gaps in the chain of custody that suggest the blood sample has been altered, the sample may be inadmissible as evidence.  However, even if an argument against the sample’s admissibility is unsuccessful, any gap in the chain of custody can be asserted to challenge the credibility of the evidence.
  10. Rate of Error by Lab:  This is a statistic that reflects the accuracy of the lab in testing its samples.  If a lab has a poor rate of error or does not report it, the credibility of the lab should be challenged.

Consult an Experienced Tucson DUI Attorney

The above intricacies are just a portion of the issues present in any DUI case.  It takes an experienced DUI attorney with a sound strategy to challenge these aspects of blood sample evidence.  If you face a DUI charge, consulting a criminal defense lawyer can ensure a fair trial.  Regardless of your blood alcohol content at the time, the above defenses as well as other criminal procedure defenses are available to be raised during or before trial.