Retrograde Extrapolation Now
While courts have been accommodating in the past, State v. Babich, changes the picture for retrograde extrapolation testimony in DWI cases.
Retrograde Extrapolation Before
Previously, North Carolina courts have liberally approved the admission of retrograde extrapolation testimony. For example, State v. Turbyfill held a field technician could testify about retrograde extrapolation using an FTA form. Even though he could not explain his calculations, it was still allowed into evidence. And in State v. Green, the court allowed the head of the FTA to testify about defendant’s specific alcohol concentration. However, the basis was assumptions about how many drinks the defendant drank before breath testing some three hours later. Rather generous in letting almost any testimony into evidence before Babich.
Retrograde Extrapolation Now
In Babich, the trial court allowed a forensic chemist to use a mathematical formula that assumed Babich was eliminating alcohol. Furthermore, he assumed an average rate for an hour and forty-five minutes before breath testing. Because no facts supported the expert’s assumptions, the court held the testimony was inadmissible under Daubert. While this decision seems like common sense, it is actually a big shift from the past in NC DUI law.
Case Facts
While speeding, Babich was stopped after running a red light around 3 am. After observing several signs of impairment, the officer arrested Babich and charged driving while impaired. Subsequently, Babich gave breath samples at 5:07 and 5:09 a.m., showing a 0.07 alcohol concentration. Rather than let it go, the officer arrested and prosecuted. So much for the “legal limit” 0.08. Subsequently, at trial, Bethany Pridgen, a forensic chemist with the Wilmington Crime Lab, testified as an expert on retrograde extrapolation. Furthermore, Pridgen testified the formula she used applies only if the person’s blood alcohol level is declining. In addition, she acknowledged that many factors affect alcohol absorption. For example, when the person last consumed alcohol, how much, and whether the person consumed food. However, Pridgen had no information about those factors and assumed Babich was in the alcohol-elimination phase when arrested.
On Appeal
Because of assumptions, Babich argued that Pridgen’s calculations were not based on sufficient facts or data. As a result, the court of appeals agreed, holding that the testimony did not satisfy the Daubert “fit” test. Hence, the testimony was not sufficiently tied to the facts of the case that would aid the jury. In addition, the court cited several court decisions from other states reaching the same conclusion on similar facts. In conclusion, the court held that facts must support an expert’s opinion. While facts can come from statements, observations, other witnesses, or circumstantial evidence, you cannot assume them. And when “at least some facts” support the expert’s assumption, the testimony is admissible. However, the jury decides what weight and credibility to give it.
