The Court acknowledges that "retrograde extrapolation" testimony constitutes reliable evidence under Rule 702 ⁽¹⁾ if the principles of the theory are applied correctly. However, the Court contends that the retrograde extrapolation analysis in this case was improperly conducted. I respectfully disagree.

The Court first contends that McDougall's testimony reflects a failure to explain the theory with any clarity. In support of this contention, the Court points to what it believes are various contradictions in McDougall's testimony. The Court finds that McDougall contradicted himself in testifying that absorption could last no longer than an hour, an hour and a half, or two hours. My reading of the testimony reveals no contradiction. McDougall testified that usually absorption would take no longer than an hour, and at most it would take an hour and a half. McDougall acknowledged a study that showed absorption taking two hours, but McDougall cautioned that the study involved relatively small amounts of alcohol (well below the legal limit) that were diluted by food. McDougall maintained that larger volumes of alcohol were not so easily diluted and were absorbed within the hour and a half time frame.

The Court also contends that McDougall contradicted himself by testifying that Mata's BAC at the time of driving would have been at least .08, then .12 or .13. But an examination of the testimony shows no contradiction. McDougall set .12 or .13 as the low end but acknowledged an "extreme situation" that could result in a lower BAC of .08.

Citing Widmark's research and other literature suggesting that the average elimination rate is .015 per hour, the Court finds fault with McDougall's testimony that the average elimination rate is .02. But earlier in its opinion the Court cites other literature that says Widmark's average is too slow. ⁽²⁾ Moreover, recent literature indicates that anything from .015 to .020 is accepted as "normal." ⁽³⁾ "Disagreements between experts about the variables and correct elimination rates to be applied go to the weight of the evidence as do the differences in the experts' credentials." ⁽⁴⁾ The Court faults McDougall for failing to acknowledge contrary opinions in the literature, but McDougall was not asked about contrary opinions. He was simply asked for his own opinions on the elimination rate. As a qualified expert, McDougall could base his opinion on what he believed to be the most accurate literature on the subject and what accords most with his experience, which, according to his testimony, included the testing of two thousand individuals. If McDougall had been questioned about the contrary literature and had failed to acknowledge it, that might be cause for concern, but such was not the case here.

The Court further argues that McDougall committed a math error by giving a high-end range of .25, when the high-end should have been a .23 given a test result of .19 and using an elimination rate of .02 per hour for two hours. But, the supposed math error seems to be eliminated if one considers that the .25 estimate was made at the motion to suppress hearing, where McDougall used the .196 base test result. McDougall testified at trial that the average elimination rate ranged from .018 to .025, although .02 was considered "normal." Adding a .025 elimination rate to .196 over two hours would yield a .246 - or .25 if one rounds up. At trial, the prosecution used the other sample as the basis for comparison, giving a base test result of .193. McDougall then calculated the high end as .23, which is consistent with the testified elimination rate of .02.

The Court also contends that McDougall assumed an elimination rate of .03 in his testimony, thereby going beyond his own stated range of elimination rates. A close examination of the testimony, however, shows that McDougall was referring to the low end of the alcohol concentration range - which is produced by measuring absorption rates, not elimination rates. McDougall clearly misspoke here when he used the word "elimination" instead of "absorption." That slip of the tongue does not mean McDougall was unable to explain retrograde extrapolation with any clarity; it simply means that McDougall is human and can be expected to make a mistake now and then. If the parties had thought it to be important, they could have corrected this slip of the tongue through questioning. And in fact, in other testimony at trial, McDougall expressly stated that a total absorption of .04 or .06 could be expected over a two hour period, which is consistent with the ".02 to .03" per hour rate given in the testimony of which the Court complains. ⁽⁵⁾

The Court finally contends that McDougall contradicted himself when he first testified that five drinks would be required to increase from below a .10 to a .19 in two hours but later testified that seven to twelve drinks would be required. But the record shows the latter testimony was in response to a hypothetical assuming a BAC "from .01 to .09." The Court contends that this range was either a stenographic error or a misstatement by the prosecutor but that the witness clearly understood the prosecutor's question to refer to the previous hypothetical involving a range of .10 to .19. It may be, however, that the prosecutor misspoke, and in so doing, confused the witness. McDougall's earlier testimony involved two hypotheticals: (1) five drinks (shots of hard liquor) to raise someone from a .10 to a .19, and (2) twelve drinks to raise someone from a .00 to a .19. McDougall may have believed that the prosecutor was referencing the latter hypothetical in giving his answer. At any rate, after McDougall's seven to twelve drink answer, the prosecutor clarified the hypothetical as coming from "below a .10 up to a .19." Such a hypothetical could include a base level of .00 through .09 with .19 as the end result - which would make McDougall's range of seven to twelve drinks consistent with his previous testimony. Moreover, if there was a contradiction, no one bothered to question McDougall about it. Had someone done so, perhaps McDougall would have supplied an explanation for the apparent disparity or explained whether he had misheard or misunderstood the hypothetical.

The trial court could have easily concluded from the evidence before it that McDougall could explain the theory of retrograde extrapolation with sufficient clarity.

The Court next contends that there were insufficient facts in the present case from which to conduct a proper retrograde extrapolation analysis. The Court lists the following non-exclusive characteristics to consider: weight, sex, typical drinking pattern, tolerance for alcohol, how much the person had to drink on the occasion, what the person drank, duration of the drinking spree, time of the last drink, and how much the person had to eat. McDougall knew that appellant was a man. Although he did not know appellant's weight, McDougall testified that his calculations had taken weight into account. Perhaps McDougall was referring to the hypothetical of a person weighing 150 pounds that was given to him at trial. If appellant's weight varied greatly from150 pounds, he could have brought that out through cross-examination and posed a hypothetical that included his actual weight.

Moreover, McDougall testified that his figures assumed a normal drinking pattern, but he was willing to explain how the estimates would change for a chug-a-lug situation. Further, McDougall testified to the top and bottom ends of the range of possible intoxication based upon the breath result of .19. His figures assumed an empty stomach because the figures for a full stomach would be closer to the tested value, and hence, within the range given. Finally, while he did not know whether appellant was in the absorption phase or elimination phase, McDougall gave figures that took both of these possibilities into account.

While McDougall's knowledge of appellant's personal characteristics was sparse, he did not attempt to arbitrarily estimate a single value for appellant's BAC. If he had done so, the Court's criticism would be well-taken. But McDougall was a very thoughtful witness. He set up a rather large range of BAC values and explained the assumptions upon which that range was based. In doing so, McDougall took into account the universe of likely factors based upon the information given. If appellant believed that McDougall had neglected to consider a particular factor or set of factors, appellant was free to pose the appropriate hypothetical and obtain a corresponding opinion. In fact, McDougall plainly said that a variety of factors could influence a person's BAC.

McDougall testified to a BAC range that, regardless of the factors involved, showed appellant was almost certainly above the legal limit. In that regard, the testimony was both reliable and helpful to the jury.

I respectfully dissent.

KELLER, Presiding Judge

Date filed: June 6, 2001

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1. Texas Rule of Evidence 702 provides:

If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education may testify thereto in the form of an opinion or otherwise.

2. Court's opinion at 20 (citing Y. Al-Lanqawi et al., Ethano Kinetics: Extent of Error in Back Extrapolation Procedures, 34 BRITISH J. OF CLINICAL PHARMACOLOGY 316, 320 (1992).

3. J. Nicholas Bostic, Alcohol-Related Offenses: Retrograde Extrapolation after Wager, 79 MICHIGAN BAR J. 668, conclusion section (June 2000).

4. Id.

5. See Court's opinion, Appendix C. Consistent with his one and a half hour time frame for absorption, McDougall indicated that the peak could have been maintained or reduced a little before arrest.