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Click here for the full text of this decision A rational trier of fact could find that a reasonable extrapolation could take place, despite the delay between the stop and testing, given this knowledge of the appellant’s personal characteristics. FACTS:The appellant was charged by information with driving while intoxicated. He filed a motion to suppress the results of his breath test. Following a hearing, the court denied his motion to suppress, and the appellant pleaded guilty to DWI. HOLDING:Affirmed. The appellant contends that the trial court erred in finding that the state’s expert was qualified to testify as an expert because his testimony regarding retrograde extrapolation was inconsistent and he did not have sufficient knowledge of the science underlying retrograde extrapolation. The Court of Criminal Appeals held in Mata v. Statethat retrograde extrapolation can be reliable in a given case, but that the expert’s ability to apply the science and explain it with clarity to the court is a paramount consideration. Mata v. State, 46 S.W.3d 902 (Tex. Crim. App. 2001). Ricky Viser, the state’s breath test expert, explained the use and methods of retrograde extrapolation in a clear and understandable manner. Viser’s seven years of employment as a technical supervisor with a background in both biology and chemistry, while not determinative of his expertise, suggests that he has the general background to perform retrograde extrapolations. He testified that he had practical experience in calculating BAC using retrograde extrapolation and had taken part in studies calculating BAC in controlled settings. Viser explained the scientific theories underlying retrograde extrapolation and demonstrated an understanding of the methodology and risks inherent in using retrograde extrapolation. Further, Viser used retrograde extrapolation to calculate BACs in response to hypothetical situations, including one in which all of appellant’s known characteristics were given. He explained how certain factors, such as whether a person had an empty or full stomach and what kind of food had been eaten, would affect how alcohol was absorbed and thus the blood alcohol level. While Viser did fail to convey to the court how Henry’s Law and Boyle’s Law applied to retrograde extrapolation, his explanation of retrograde extrapolation itself was not affected. Viser’s testimony was useful for a factfinder to properly understand how retrograde extrapolation was used and possible problems that could arise when making an extrapolation. Therefore, the trial court did not abuse its discretion by allowing Viser to testify. The appellant argues that there was insufficient factual evidence on which to base an extrapolation and thus the probative value of the evidence was outweighed by the prejudicial effect. As held in Mata, a court evaluating the reliability of a retrograde extrapolation should consider: a. the length of time between the offense and the test(s) administered; b. the number of tests given and the length of time between the tests; and c. whether, and if so, to what extent, individual characteristics of the defendant were known to the expert in providing his extrapolation, including, but not limited to, the person’s weight and gender, the person’s typical drinking pattern and tolerance for alcohol, how much the person had to drink on the day or night in question, what the person drank, the duration of the drinking spree, the time of the last drink, and how much and what the person had to eat before, during, or after the drinking. However, Mata states, “not every single personal fact about the defendant must be known to the expert in order to produce an extrapolation with the appropriate level of reliability.” Thus, using retrograde extrapolation to determine a person’s BAC level after an arrest requires that the person calculating the retrograde extrapolation have sufficient known facts to determine what the driver’s probable breath test score was at the time of driving. In the present case, the appellant stipulated to the time of his last drink, his weight and height, the time of the breath tests, the results of the breath tests, his last meal prior to being stopped, and the time of that meal. The breath tests were performed two and one-half hours after appellant’s last drink-an hour and one-half after appellant was stopped. The longer the period between the stop and the BAC test tends to diminish the reliability of the tests. However, a significant number of appellant’s personal characteristics were known, both those facts stipulated to and facts used in each individual calculation, which would tend to increase the reliability of the extrapolation. A rational trier of fact could find that a reasonable extrapolation could take place, despite the delay between the stop and testing, given this knowledge of the appellant’s personal characteristics. The court holds that there was sufficient evidence on which to base an extrapolation and that the probative value was not outweighed by any prejudicial effect of Viser’s testimony. OPINION:Nuchia, J.

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