Motion to exclude expert testimony

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§ OF



COMES NOW, JOHN DOE, Defendant in the above styled and numbered cause, and moves the Court to order the State not to refer to any evidence or to elicit, through its expert witness, ________________, any testimony regarding retrograde extrapolation or any evidence or testimony regarding Defendant’s purported blood alcohol content at the time of the alleged offense, and in support of said motion, would respectfully show the Court as follows:


On April 13, 2004, this Court held a hearing at which two of the State’s witnesses testified regarding scientific evidence and expert testimony. One of the State’s witnesses, Dr. James Martin, testified regarding the results of testing done on blood that was drawn from Defendant on October 26, 2001. On cross examination by the undersigned counsel, when asked if he could testify reliably as to what Defendant’s blood alcohol content (BAC) was at the time of the alleged offense, 2:23 a.m., Dr. Martin replied, “I can say that more than likely it was higher at that time, because of the time period that we’re talking about, unless you give me other conditions that would tend to dispel that, but I couldn’t tell you exactly what that level would be without being given more information.” (R.R. 89–90). When questioned further about what he based his opinion on, Dr. Martin replied that his opinion was “...[b]ased on the time period.” (R.R.. 90). Dr. Martin further testified, “...more than likely it would be higher because more than likely he would be in the elimination phase...As opposed to alcohol just sitting there yet to be absorbed unless you gave me a specific incident, or that would be a possibility.” Id.


Said proffered testimony, which amounts to no more than blatant speculation, is inadmissible under the Court of Criminal Appeals’ decision in Mata v. State, 46 S.W.3d 902 (Tex. Crim. App. 2001), overruled in part on other grounds by Bagheri v. State, 119 S.W.3d 755 (It is not harmeless error analysis when it is unclear whether the extrapolation evidence to prove on way of being intoxicated might have seriously affected the jury’s ability to deliberate upon that core element of intoxication, whether by “loss of normal use” or “per se.”). In Mata, the Court of Criminal Appeals, en banc, addressed a similar situation where the State’s expert testified regarding the theory of retrograde extrapolation. Id. at 904. Said expert then testified that it was his opinion that the defendant’s BAC was over the legal limit at the time of the offense. Id. at 905.

In examining the issues, the Court of Criminal Appeals first mandated that if an expert witness is to testify regarding retrograde extrapolation, it is a paramount consideration that he must first be able “ apply the science and explain it with clarity to the court....” Id. at 916. Additionally, the expert must demonstrate some understanding of the difficulties inherent in attempting a retrograde extrapolation. Id. Finally, the expert “...must be able to clearly and consistently apply the science.” Id.

In the present case, the State has utterly failed to provide any evidence or elicit any testimony from Dr. Martin regarding the above requirements. As such, any testimony regarding attempted retrograde extrapolation or an opinion regarding Defendant’s BAC should be excluded.

Moreover, even if Dr. Martin were able to testify in compliance with the above requirements, his “opinion” should still be excluded, according to the principles established in Mata. The Court of Criminal Appeals established that the trial court, in evaluating the reliability of the proposed retrograde extrapolation, should also consider (a) the length of time between the alleged offense and the given test(s); (b) the number of tests actually administered; and (c) whether, and if so, to what extent, any individual characteristics of the defendant were known to the expert when making the extrapolation. Id. The Court went on to list a non-exclusive list of pertinent characteristics, such as weight, gender, typical drinking pattern, tolerance for alcohol, how much alcohol was consumed on the date in question, what was consumed, the duration of drinking, the time of the last drink and what was eaten and when. Id.

The Court then stated that it would be possible for an expert to reliably extrapolate with only limited knowledge of the personal characteristics and behaviors of the defendant “...if the State had more than one test, each test a reasonable length of time apart, and the first test were conducted within a reasonable time from the time of offense....” Id. (emphasis added). However, in the instance where a single test was conducted some time after the offense, reliable extrapolation could be performed “...only if the expert had knowledge of many personal characteristics and behaviors of the defendant.” Id. (emphasis added).

While there are two results in the instant case, the gathering of the results occurred a mere nineteen to twenty minutes apart, and according to Dr. Martin, such a time interval would not make much difference in the results. (R.R. 81). While the Court of Criminal Appeals did not indicate what a “reasonable” length of time would be between “tests,” Dr. Martin’s own testimony illustrates the inadequacy of an interval of approximately twenty minutes.

Moreover, by his own admission, Dr. Martin acknowledged that he did not have enough information to properly extrapolate in the instant case. (R.R. 89). As such, Dr. Martin should not be allowed to circumvent the principles established in Mata by simply giving a general opinion that Defendant’s BAC was likely above 0.08 g/100 ml at the time of the accident, or that it was higher at the time of driving than the level detected by the subsequent test. If such testimony were allowed, it would fly in the face of Mata and the requirements established therein, defying the instruction of the Texas Court of Criminal Appeals.


Based on the above arguments, Defendant would submit that said proffered testimony is irrelevant under Rule 401 of the Texas Rules of Evidence (TRE). As said testimony is scientifically unreliable and baseless in foundation, it would not have any tendency to make the existence of any fact that is of consequence to the determination of the action (in this case Defendant’s BAC at the time of the accident) more probable or less probable than it would be without said evidence. As such, it should be excluded under Rule 402, TRE, which prohibits the introduction of inadmissible evidence.

Further, should the Court find that said offered testimony is relevant, its introduction should be precluded by Rule 403, TRE, which allows for the exclusion of evidence if the probative value of said evidence is substantially outweighed by the danger of unfair prejudice, confusion of the issues or misleading the jury. In the case at bar, said proffered testimony, if introduced, would certainly lead to unfair prejudice against Defendant, as the jury would be unfairly influenced by such an opinion from a State’s witness who has been qualified as an expert. As the opinion has no basis in fact or science, the jury would be misled as to the validity and scientific basis of the opinion, and no cross-examination by defense counsel would be able to remove the unduly harmful effects or cure the unfair prejudice of presenting the jury with an ill-founded expert opinion.


Said testimony should be excluded, because it is based upon illegally obtained evidence. Corporal Walter Scott, at least at one point in his testimony, stated that he did not have probable cause to arrest Defendant in this matter when Defendant was at the hospital and in fact never arrested Defendant at that time. As such, the obtaining of the sample was obtained in contravention of §724.012 of the Texas Transportation Code, and any alleged acquiescence in the obtaining of said sample occurred only after Corporal Scott misstated the law and coerced Defendant into agreeing to provide a sample.

WHEREFORE PREMISES CONSIDERED, Defendant would respectfully request that this Court prohibit the State from introducing any evidence or eliciting testimony from Dr. James Martin regarding any opinion as to what Defendant’s BAC was at the time of the accident, whether he believes Defendant’s BAC was higher than 0.08 g/100ml at the time of the accident and whether he believes Defendant’s BAC was higher at the time of the accident than the level detected by any subsequent test.

Respectfully Submitted


On December_________, 200___, a true and correct copy of the above and foregoing Motion to Exclude Expert Testimony was hand-delivered or mailed, postage prepaid, to the _________ Attorney of__________ County, Texas.

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