Last month we introduced the toxicological aspects of cross-examining the retrograde extrapolation expert in DWI trials. Now, an understanding of toxicology will promote our error preservation before the State’s expert attempts to bamboozle the jury with opinions about the client’s driving time BAC. As a bonus, this process will also assist the defense lawyer develop meaningful cannon fodder for cross-examination if the trial court rules the extrapolation evidence admissible.

Our most powerful weapon in error preservation is TEX. R. EVID. 705(b). Rule 705(b) permits us to voir dire an expert outside the jury’s presence regarding their opinions and the factual basis for those opinions. Equally important, before scientific evidence is admissible a trial court must conduct a hearing to determine whether the proponent of the evidence has established its reliability using Kelly v. State, 824 S.W.2d 568 (Tex. Crim. App. 1992). Also see, Jackson v. State, 17 S.W.3d 664 (Tex. Crim. App. 2000); TEX. R. EVID. 702. One way to obtain a 705(b) hearing is by filing a motion in limine prior to trial requesting a hearing if the State intends to elicit retrograde extrapolation evidence. Get a ruling to assure the prosecutor is on notice and to avoid an ambush. Otherwise, approach the bench once the State’s expert takes the stand and inform the court you want a 705(b) hearing if extrapolation evidence becomes an issue. And remember this . . . sometimes a prosecutor will not ask their expert about extrapolation on direct examination. Crafty prosecutors may wait. If you open the door on cross examination, then you’ve waived error and you are screwed on re-direct. So be careful!

Once the jury retires ask for an offer of proof regarding the expert’s opinion and the facts they intend to use to support it. The prosecutor may simply propound a hypothetical to the expert using facts developed from the trial. They then ask for an opinion about your client’s BAC at the time of driving. After the offer of proof you may take the expert on voir dire. Tie them down to every fact and circumstance used to support their opinion. Use Mata v. State, 122 S.W.3d 813 (Tex. Crim. App. 2003) as a guide to bullet-point the salient facts required before proffering a retrograde extrapolation opinion. In addition to aiding your objections, this voir dire can help you develop material for cross-examination once the jury returns. Further, before extrapolation evidence is admissible it must meet three reliability criteria. First, the underlying scientific theory must be valid. Next, the technique applying the theory must be valid. And lastly, the technique must have been properly applied on the occasion in question. Kelly, supra. The burden is on the proponent to prove admissibility by clear and convincing evidence. Fuller v. State, 827 S.W.2d 919 (Tex. Crim. App. 1992). Moreover, seven factors should be considered by the trial court in deciding whether the reliability criteria have been satisfied: (1) the extent to which the underlying theory and technique were accepted as valid by the relevant scientific community; (2) the qualifications of the expert testifying; (3) the existence of literature supporting or rejecting the underlying scientific theory and technique; (4) the potential rate of error in the technique; (5) the availability of other experts to test and evaluate the technique; (6) the clarity with which the underlying scientific theory and technique can be explained to the court; and (7) the experience and skill of the person applying the technique. Kelly at 573. During your 705(b) hearing ask the expert about each of these factors and determine their depth of knowledge. If the expert refers to studies, ask to see them. I have yet to read a study I cannot distinguish from the facts of my case. If they don’t have the studies on hand, consider creating an impression with your jury the expert was bolstering their opinions without providing you a fair opportunity to question them. Again, this voir dire process can provide excellent material for cross-examination if the trial court rules the extrapolation opinion is admissible.

Once you’ve extracted everything possible from the expert, object to their extrapolation testimony as follows: (1) Object under Kelly and Mata that the State failed to prove by clear and convincing evidence the underlying theory of retrograde extrapolation was valid, that the technique applying the theory was valid, and that the technique was properly applied in your case. GET AN ADVERSE RULING; (2) Include objections to the lack of qualifications of the expert, the lack of clarity with which the expert explained the technique and theory, and the lack of skill and experience of the expert. GET AN ADVERSE RULING; (3) Object to the relevance of the opinion under TEX. R. EVID. 401 and 402. GET AN ADVERSE RULING; (4) Then object under TEX. R. EVID. 403. GET AN ADVERSE RULING. Furthermore, ask the court to articulate their Rule 403 balancing test on the record. Lastly, be prepared to articulate harm if the court admits the testimony. This is not necessary to preserve error but may help the lawyer on appeal if a conviction results.

You are now fully armed to attack retrograde extrapolation and preserve error in your next DWI trial. Regularly study the toxicology as those principles give you the best opportunity to challenge the expert’s opinion. Don’t open the door to retrograde extrapolation and waive error. Use Rule 705(b) as an indispensable tool for extracting information from the expert using Kelly and Mata to develop material for your cross-examination. Get adverse rulings. And above all . . . have fun and good luck!


(“Off the Back” featured in the “Voice For The Defense” January/February 2017)

Stephen Gustitis is a criminal defense lawyer in Bryan-College Station. He is Board Certified in Criminal Law by the Texas Board of Legal Specialization. He is also a husband, father, and retired amateur bicycle racer.

“Off the Back” is an expression in competitive road cycling describing a rider dropped by the lead group who has lost the energy saving benefit of riding in the group’s slipstream. Once off the back the rider struggles alone in the wind to catch up. The life of a criminal defense lawyer shares many of the characteristics of a bicycle rider struggling alone, in the wind, and “Off the Back.” This column is for them.

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