In any criminal or motor vehicle prosecution, the State bears the burden of proof. Accordingly, when the State seek to introduce blood test results in a DWI/DUI prosecution, the State has the burden of establishing the reliability of those results.
The Court will typically conduct what is known as a 104(a) hearing on the admissibility of the blood work. This hearing should begin by determining whether the blood was drawn within a reasonable time after the defendant operated a motor vehicle. The police officer must also testify that he or she had probable cause to order the blood to be drawn.
Next, the officer will typically testify that he or she witnessed the blood be drawn by an authorized medical professional. It is important to cross-examine the officer as to whether an alcohol or betadine swab was used during the draw since an alcohol swab can obviously contaminate the result.
Under current case law, the individual who conducted the draw can be dragged into court and cross-examined. Defense attorneys should therefore object to the admissibility of any reports or certificates generated by this person in a timely manner in order to preserve the ability to conduct cross-examination.
Testimony should also be adduced establishing an unbroken chain of custody of the blood work to ensure that the results being received into evidence are actually those drawn from the defendant.