Challenging DUI Blood Evidence Part 4: Sources of Error in Blood Testing

Being able to challenge DUI blood evidence effectively is one of the ways The McShane Firm separates itself from the rest of the crowd in Pennsylvania.  Our attorneys are experienced at exposing the weaknesses in the government’s case and challenging its evidence.  DUI blood testing inherently has a number of sources of error that can be found upon careful investigation by a qualified attorney.

Sources of Error in DUI Blood Testing

    1. Bad Labs– Under-trained, overworked staff who’s focus is on getting any ” result” rather than getting the correct result.  These types of technicians can sometimes skew the results of a toxicology test to support the prosecution when, in reality, the result is not there.  This coupled with a lack of oversight and corrective action is a recipe for disaster in a forensics laboratory. There are many examples of this in the news such as the horrible criminal labs in Indiana.
    2. Contamination– Blood tubes are very sensitive and need to be handled in a very specific way.  If there is deviation from these authorized handling procedures, the results become doubtful and any result gathered loses its scientific value.  Some common examples of mishandling of blood tubes are:
      • No clear chain of custody
      • Procedures not documented
      • Tubes transported by normal carriers like FedEx
      • Blood Tubes stored in non-ideal conditions
      • Lack of proper refrigeration
      • Shaking of the tubes
      • Contamination of the tubes and the blood inside
      • Switching of the tubes while in transport

      Any of the above can lead to contamination and raise doubts about the validity of the test results.

    3. Calibration– In a scientific laboratory, the machines and instruments need to be properly maintained and set to ensure they are working properly.  Just think about the common bathroom weight scale.  There is a small dial on it to calibrate it to zero and if this is not done periodically, it will over or under report your weight.  The same is true for high tech scientific instruments.  They need to be calibrated properly and because they are dealing with very small amounts, any variance can make a big difference in the end result.  This is a very common source of error.
    4. Mixing up the samples– When the correct procedures are not followed, blunders happen.  It is not at all uncommon to see that the crime lab test someone else’s blood sample.  This is why defense lawyers need to be very diligent in making sure proper handling and documentation procedures were followed.
    5. Documentation– Even if the testing was done up to standard, it has no scientific backing without the proper documentation. We call this verification.  Without documentation, the results are based on an “act of trust” which is not allowed in court and is against the scientific method.

These are some of the common sources of error that are found in DUI blood tests.  These problems are rampant all over the country and even here locally in Pennsylvania DUI cases.  If you have doubts about your Pennsylvania DUI blood test then call the PA DUI attorneys at The McShane Firm at 1-866-MCSHANE.

Justin McShane

PA DUI attorney Justin J. McShane is the President/CEO of The McShane Firm, LLC - Pennsylvania's top criminal law and DUI law firm. He is the highest rated DUI attorney in PA as rated by Justin McShane is a double Board certified attorney. He is the first and so far the only Pennsylvania attorney to achieve American Bar Association recognized board certification in DUI defense from the National College for DUI Defense, Inc. He is also a Board Certified Criminal Trial Advocate by the National Board of Trial Advocacy, a Pennsylvania Supreme Court Approved Agency.

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