Defense expert can not rely on preliminary breath test result
In most states the preliminary breath test (PBT) result is not admissible in DUI cases. The PBT is typically inadmissible because it is inaccurate. However, when a PBT is exonerating, and an evidentiary breath or blood test is incriminating, the defense may want the PBT admitted into evidence.
The Opinion: The Court of Appeals of Wisconsin in State v. Fisher, decided against the admission of a defense-favorable PBT on 9/10/08.
Quotes: A general description of the difference between a PBT and an evidentiary breath test:
Unlike the Intoximeter, the PBT is not tested for accuracy either immediately before or after a test. The intoximeter is a “quantitative” test and the PBT is a “qualitative” test.
Clearly, the former test calls for an accurate “measurement” that is, after all, the definition of the word “quantitative”-something “involving the measurement of quantity or amount.” Webster's Third New Int'l Dictionary 1859 (3d ed.1993). A qualitative analysis, as any chemistry major would know, merely determines the constituents of a substance without any regard to the quantity of each. Id. at 1858. Thus, as succinctly defined in the administrative code, the qualitative breath test is for the purpose of determining only whether alcohol is present or not.
Quotes: Why the defense expert was not allowed to proffer an opinion based on the PBT:
Dr. Steele can compare the PBT result with a blood test result 100 times and be convinced as to the reliability of his absorption curve analysis. But is his analysis valid? We must answer the question “no” because Fischer's PBT result is not an empirically tested measurement.
Why allow an expert, one with a science background, to rely on a test whose accuracy at the time of the test cannot be authenticated as a foundation for an opinion? That makes no sense.
Discussion: In DUI cases experts often “backdoor” inadmissible evidence into their opinion. Experts on both sides of the “v” do it. Both prosecutors and defense lawyers at times knowingly allow and even encourage such testimony. In this case, as an example, a defense lawyer could ask the expert generally:
“Given your review of the materials in this case and your whole knowledge of the facts, do you have an opinion as to whether it is possible that Fisher could have been below the legal limit.”
Without qualifying that the expert can only form such an opinion by presuming that the PBT is accurate (an assumption that no honest expert can make), the answer would be garbage and the legal ethics of the question questionable.
