Defenses related to the admissibility of the prosecution’s blood testing evidence.
For a blood test to be admissible as evidence, the prosecutor has to demonstrate the reliability of the test. This might require putting forth various witnesses.
For the results of the State’s test to be admissible, the State must show that it was performed in such a way that the results obtained should be considered accurate and that the biological substance tested came from you and no one else.
The first area of proof focuses upon whether the machine itself was properly calibrated, whether the test was run correctly and run by someone capable, trained and authorized to operate the machine.
Even if the blood test results being offered as evidence against you were drawn as a part of a medical evaluation in a hospital, rather than those drawn at the express direction of the police for evaluation in a crime lab, the testing must still have been done in compliance with some recognized standards.
The second area of inquiry focuses on the State’s ability to establish the chain of custody for your sample. Here the issue is whether the manner in which the police gathered, secured, preserved and tested the sample of blood, breath or urine can be said to have eliminated any possibility of contamination or other interference with obtaining a convincingly accurate measurement.
Your attorney focuses upon whether the sample was collected properly, whether the collection tubes were of the correct types, whether your arm was swabbed with a non-alcoholic pad, whether the nurse properly inverted the vial of blood before sealing the package for shipment to the crime lab, and similar issues that involve the “integrity” of the sample.
If the evidence demonstrates that the police did not properly gather, secure, preserve and test the sample of blood, breath or urine, the judge may agree with your lawyer’s objection to the test result being presented to the jury.
Instead, the judge may exclude that evidence from your trial. Such an exclusion by a trial court often ends the case, due to a “lack of evidence” to support the DUI-DWI charge against you.
Even when grossly improper handling of your blood sample is shown by your attorney, the lab results might not be automatically excluded from evidence at trial. Instead, the judge might decide that evidence of any discrepancies in the chain of custody may affect the weight that the jury decides to give to that evidence, and not cause the test results to be excluded.