Fourth Court of Appeals

San Antonio, Texas

MEMORANDUM OPINION

No. 04-19-00385-CR

Gustavo CUELLAR, Jr.,

Appellant

v.

The STATE of Texas,

Appellee

From the 451st Judicial District Court, Kendall County, Texas

Trial Court No. 6255

Honorable Kirsten Cohoon, Judge Presiding

Opinion by: Rebeca C. Martinez, Justice

Sitting: Rebeca C. Martinez, Justice 

Irene Rios, Justice

Beth Watkins, Justice

Delivered and Filed: August 19, 2020

AFFIRMED

Gustavo Cuellar appeals his conviction for the offense of driving while intoxicated, third 

or more. See TEX. PENAL CODE ANN. §§ 49.04(a), 49.09(b)(2). In two issues, Cuellar argues the 

trial court erred by (1) admitting unreliable retrograde extrapolation evidence of his blood-alcohol 

content and (2) denying his request for a jury instruction pursuant to Texas Code of Criminal 

Procedure Article 38.23. We affirm the trial court’s judgment. 
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BACKGROUND

On May 2, 2017, Cuellar was indicted for driving while intoxicated, third or more. The 

indictment alleged that, on or about February 24, 2017, Cuellar operated a motor vehicle while 

intoxicated by not having the normal use of his mental or physical faculties by reason of the 

introduction of alcohol into his body, or by having an alcohol concentration of at least 0.08. 

A jury trial was conducted, and the jury found Cuellar guilty of the charged offense. 

Thereafter, Cuellar and the State entered into a plea agreement as to Cuellar’s punishment. The 

trial court followed the parties’ plea agreement and assessed punishment at four years’ 

confinement, to be served in a therapeutic community. Cuellar appeals. 

RETROGRADE EXTRAPOLATION

In his first issue, Cuellar argues the trial court abused its discretion by admitting unreliable 

retrograde extrapolation evidence of his blood-alcohol content. 

The party offering scientific evidence “must demonstrate by clear and convincing evidence 

that the evidence is reliable.” Mata v. State, 46 S.W.3d 902, 908 (Tex. Crim. App. 2001). 

Reliability may be established “by showing the validity of the underlying scientific theory, the 

validity of the technique applying the theory, and [the] proper application of the technique on the 

occasion in question.” Id. It is the trial court’s responsibility “to determine whether [the] proffered 

scientific evidence is sufficiently reliable and relevant to assist the jury.” Id. A trial court’s 

decision to admit scientific evidence is reviewed for an abuse of discretion. Id. The evidentiary 

ruling “must be upheld so long as it is ‘within the zone of reasonable disagreement.’” Wheeler v. 

State, 67 S.W.3d 879, 888 (Tex. Crim. App. 2002) (quoting Montgomery v. State, 810 S.W.2d 372, 

391 (Tex. Crim. App. 1990)). 

“Retrograde extrapolation is the computation back in time of [an individual’s] bloodalcohol level—that is, the estimation of the [blood-alcohol] level at the time of driving based on a 
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test result from some later time.” Mata, 46 S.W.3d at 908–09. The science of retrograde 

extrapolation may be reliable under certain circumstances. See id. at 916. The expert’s ability to 

clearly and consistently apply the science and explain it with clarity is a paramount consideration. 

Id. In evaluating the reliability of an expert’s application of retrograde extrapolation in a given 

case, a court should consider the following factors: 

(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 each test; and (c) whether, 

and if so, to what extent, any individual characteristics of the defendant were known 

to the expert in providing his extrapolation. These characteristics and behaviors 

might include, but are 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 either 

before, during, or after the drinking.

See id. at 916. The Texas Court of Criminal Appeals set forth the following guidelines for 

balancing these factors: 

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 the offense, 

then an expert could potentially create a reliable estimate of the defendant’s BAC 

with limited knowledge of personal characteristics and behaviors. In contrast, a 

single test conducted some time after the offense could result in a reliable 

extrapolation only if the expert had knowledge of many personal characteristics and 

behaviors of the defendant. Somewhere in the middle might fall a case in which 

there was a single test a reasonable length of time from the driving, and two or three 

personal characteristics of the defendant were known to the expert.

Id. at 916–17. 

Here, Cuellar does not challenge the science of retrograde extrapolation, nor does Cuellar 

challenge Pierce’s qualifications to perform a retrograde extrapolation. Rather, Cuellar contends 

Pierce’s testimony was unreliable because Pierce assumed certain facts that were contrary to the 

evidence and Pierce then used those erroneous assumptions in his retrograde extrapolation 

calculation. Cuellar also argues that Pierce did not know a sufficient number of his personal 

characteristics and behaviors to perform a reliable retrograde extrapolation. 
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On February 24, 2017 at approximately 8:00 p.m., surveillance footage from a gas station 

showed Cuellar’s vehicle entering the gas station parking lot. Officer Morales of the Boerne Police 

Department testified that he observed Cuellar’s vehicle “parked illegally over a couple of parking 

lanes” in the gas station parking lot. Officer Morales observed the vehicle for approximately thirty 

minutes, and, in his observation, he noted that the vehicle remained on, and no one entered or 

exited the vehicle. Officer Morales made the decision to approach the vehicle and determine if its 

occupants were okay. At approximately 8:30 p.m., Officer Morales initiated contact with Cuellar 

and, after concluding that Cuellar was intoxicated, arrested him for driving while intoxicated.1

 

Thereafter, Cuellar was transported to Boerne Methodist Hospital, where one blood test was 

administered at 10:00 p.m. Because a single blood test was administered some time after the 

offense, Pierce needed to know “many” of Cuellar’s personal characteristics to reliably perform a 

retrograde extrapolation. See Mata, 46 S.W.3d at 916–17; see also Bhakta v. State, 124 S.W.3d 

738, 742 (Tex. App.—Houston [1st Dist.] 2003, pet. ref’d) (“The longer the period between the 

stop and the BAC test tends to diminish the reliability of the test[].”).

Pierce assessed the time of Cuellar’s last drink and the time of Cuellar’s last meal based on 

a questionnaire Cuellar filled out after his arrest. Based on the information that Cuellar had his 

last drink at 6:00 p.m. and his last meal at noon, Pierce assumed that Cuellar’s blood draw at 10:00 

p.m. was taken when Cuellar was in the elimination phase of his alcohol consumption.2

 The results 

of Cuellar’s blood test showed that Cuellar had a blood-alcohol concentration of .257 at 10:00 p.m. 

Based on the assumption that Cuellar was in the elimination phase at the time of his blood draw, 

1 Officer Morales testified that he originally arrested Cuellar for public intoxication, but that his supervisor ordered 

him to arrest Cuellar for driving while intoxicated. 

2 “As alcohol is consumed, it passes from the stomach and intestines into the blood, a process referred to as 

absorption. . . . At some point after drinking has ceased, the person’s BAC will reach a peak. After the peak, the BAC 

will begin to fall as alcohol is eliminated from the person’s body. The body eliminates alcohol through the liver at a 

slow but consistent rate.” Mata, 46 S.W.3d at 909. 
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Pierce testified that he could reliably perform an extrapolation back to the time of the offense.

3

 

Pierce estimated that Cuellar had a blood-alcohol concentration ranging from .272 to .302 at 8:30 

p.m., with an average blood-alcohol concentration of .287. Pierce estimated that Cuellar had a 

blood-alcohol concentration ranging from .277 to .317 at 8:00 p.m., with an average blood-alcohol 

concentration of .297. 

Cuellar contends Pierce’s reliance on 6:00 p.m. as the time of Cuellar’s last drink is 

contrary to the evidence because an open, three-quarters full, cold can of beer was found in 

Cuellar’s vehicle at the time of his arrest. According to Cuellar, this evidence indicates that his

last drink occurred sometime between 8:00 p.m. and 8:30 p.m. Therefore, Cuellar contends Pierce

improperly assumed that Cuellar was in the alcohol elimination phase at the time of his blood 

draw, thereby rendering his retrograde extrapolation calculation unreliable. 

“[T]he trial court does not abuse its discretion by allowing an expert to base testimony 

upon an assumption if there is a factual basis for the assumption in the record.” Bigon v. State, 

252 S.W.3d 360, 367 (Tex. Crim. App. 2008). Here, Pierce based his assumption that Cuellar was 

in the alcohol elimination phase at the time of his blood draw on Cuellar’s statement that he had 

his last drink at 6:00 p.m. In his DWI questionnaire, which was admitted as evidence, Cuellar 

stated that he had his last drink at 6:00 p.m. Although an open, three-quarters full, cold can of 

beer was found in Cuellar’s vehicle at the time of his arrest, the trial court could have reasonably 

credited Cuellar’s statement that his last drink was at 6:00 p.m. See id. (recognizing that the trial 

court is “in the best position to judge the credibility of the witnesses” when deciding whether to 

3 Pierce testified that if Cuellar’s last drink was between 8:00 p.m. and 8:30 p.m., it would affect his calculation 

because it would mean that Cuellar may have been in the absorption phase of his alcohol consumption at the time of 

his blood draw, instead of his elimination phase. If this were the case, Pierce stated, his current extrapolation 

calculation would be “overestimated.” Pierce was not asked to quantify by how much his calculation would be 

overestimated. 
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admit expert testimony based upon an assumption). Because there is a factual basis for Pierce’s 

assumption that Cuellar was in the alcohol elimination phase, the trial court’s decision to allow

Pierce’s retrograde extrapolation testimony based on that assumption was not an abuse of 

discretion. See id. (concluding trial court did not abuse its discretion in allowing retrograde 

extrapolation testimony that was based on the expert’s assumption that appellant was in the alcohol 

elimination phase because the expert based his assumption on medical records that stated when 

appellant had his last meal and drink). 

Cuellar also argues that Pierce did not know a sufficient number of his personal 

characteristics and behaviors to perform a reliable retrograde extrapolation. 

A significant number of Cuellar’s personal characteristics and behaviors were known to 

Pierce, such as (1) Cuellar’s gender, height, and weight; (2) that Cuellar “drank a couple” of drinks 

on the night in question; (3) that Cuellar’s last drink was at 6:00 p.m.; (4) that Cuellar’s last meal 

was a sandwich, which he ate around noon; (5) the time of the offense, which was approximately 

between 8:00 p.m. and 8:30 p.m.; (6) that Cuellar’s blood was drawn at 10:00 p.m.; and (7) that 

Cuellar’s blood results showed that Cuellar had a blood-alcohol concentration of .257 at 10:00 

p.m. The trial court could have reasonably determined that Pierce had sufficient knowledge of 

Cuellar’s personal characteristics and behaviors to reliably perform a retrograde extrapolation. 

See, e.g., Bhakta, 124 S.W.3d at 742 (holding that, despite the significant delay between the traffic 

stop and the breath test, the expert had sufficient evidence on which to base a reliable extrapolation 

because the expert knew appellant’s height and weight, appellant’s last meal prior to being 

stopped, the time of appellant’s last drink and meal, and the time and results of appellant’s breath 

test); see also Mata, 46 S.W.3d at 916 (“[N]ot 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.”). 
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On this record, we conclude that the trial court’s decision to admit Pierce’s expert 

testimony on retrograde extrapolation was within the zone of reasonable disagreement and was, 

therefore, not an abuse of discretion.

JURY INSTRUCTION

In his second issue, Cuellar argues the trial court erred by denying his request for a jury 

instruction pursuant to Texas Code of Criminal Procedure Article 38.23. 

Article 38.23(a) provides:

No evidence obtained by an officer or other person in violation of any provisions 

of the Constitution or laws of the State of Texas, or of the Constitution or laws of 

the United States of America, shall be admitted in evidence against the accused on 

the trial of any criminal case.

In any case where the legal evidence raises an issue hereunder, the jury shall be 

instructed that if it believes, or has a reasonable doubt, that the evidence was 

obtained in violation of the provisions of this Article, then and in such event, the 

jury shall disregard any such evidence so obtained.

TEX. CODE CRIM. PROC. ANN. art. 38.23(a). To be entitled to a jury instruction under article 

38.23(a), the defendant must demonstrate that: (1) the evidence heard by the jury raises an issue 

of fact; (2) the evidence on that fact is affirmatively contested; and (3) the contested fact issue is 

material to the lawfulness of the challenged conduct in obtaining the evidence. Madden v. State, 

242 S.W.3d 504, 510 (Tex. Crim. App. 2007). “There must be a genuine dispute about a material 

fact.” Id. “If there is no disputed factual issue, the legality of the conduct is determined by the 

trial judge alone, as a question of law.” Id.

Cuellar requested the following jury instruction pursuant to article 38.23: 

Our law provides that a warrantless arrest is lawful if it is made by an officer 

possessing probable cause to believe that an offense was occurring within the 

officer’s presence. No evidence obtained by an officer as a result of an unlawful 

warrantless arrest of a person may be admitted against that person at trial. 

Therefore, if you find from the evidence that on February 24th, 2017, Officer 

P[ablo] Morales arrested the defendant for being intoxicated while operating a 

motor vehicle in a public place, and you further find that the officer did not have 
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probable cause to execute that arrest, or if you have a reasonable doubt whether the 

officer had probable cause, you will disregard the evidence seized as a result of that 

arrest and will not consider that evidence for any purpose whatsoever. 

Probable cause exists for the purposes when the facts and the circumstances within 

the officer’s personal knowledge and of which the officer has reasonably 

trustworthy information would be sufficient to lead a person of reasonable caution 

to believe that an offense was being committed or had been committed and that the 

person to be arrested was linked with the commission of that offense.

The proposed instruction does not ask the jury to decide a disputed factual issue. See id. at 511 

(“It is the trial judge who decides what quality and quantum of facts are necessary to establish 

‘reasonable suspicion.’ Only if one or more of those necessary facts are disputed does the judge 

ask the jury to decide whether the officer’s belief in those facts was reasonable.”). Whether Officer 

Morales had “probable cause” to arrest Cuellar for driving while intoxicated is a question of law 

for the trial court, not a question for the jury. See id. (“The jury . . . is not an expert on legal terms 

of art or the vagaries of the Fourth Amendment. It cannot be expected to decide whether the 

totality of certain facts do or do not constitute [“probable cause” or] “reasonable suspicion” under 

the law.”). Thus, the trial court did not err by refusing to include Cuellar’s proposed article 

38.23(a) instruction. See id. at 509–10 (stating an article 38.23(a) jury instruction is limited to 

disputed issues of fact). 

In his brief, Cuellar claims a dispute of fact existed between Officer Morales’s testimony 

at trial and Officer Morales’s affidavit for a warrant for a mandatory blood draw. At trial, Officer 

Morales testified that he observed Cuellar’s vehicle “parked illegally over a couple of parking 

lanes” in the gas station parking lot. After approximately thirty minutes, Officer Morales 

approached the vehicle to determine if its occupants were okay. Upon approaching the vehicle, 

Officer Morales noted that Cuellar was in the driver’s seat and that Cuellar was the sole occupant 

of the vehicle. Officer Morales knocked on the vehicle’s window multiple times in an attempt to 

get Cuellar’s attention, but Officer Morales stated Cuellar looked at him with a blank stare. Officer 
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Morales stated that because Cuellar was not rolling his window down in response to his knocks, 

he opened Cuellar’s vehicle door. Officer Morales’s affidavit for a warrant for a mandatory blood 

draw mirrors his trial testimony; however, in his affidavit, Officer Morales makes no mention of 

Cuellar’s “illegal parking.” Thus, according to Cuellar, a dispute of fact exists as to whether 

Officer Morales approached his vehicle for “illegal parking.” 

“To raise a disputed fact issue warranting an Article 38.23(a) jury instruction, there must 

be some affirmative evidence that puts the existence of that fact into question.” Id. at 513. Here,

although the affidavit omits Cuellar’s “illegal parking,” there is no affirmative evidence that puts 

the fact that Officer Morales approached Cuellar’s vehicle for “illegal parking” in dispute. Cf. id.

at 513 (“[O]ne issue was whether appellant exceeded the speed limit of 55 m.p.h. through a 

construction site, giving Officer Lily a reasonable suspicion to stop him. If Officer Lily testifies 

that appellant did speed and Witness Two (or appellant) testifies that he did not speed, this disputed 

factual issue must be submitted to the jury.”); see also Hailey v. State, 413 S.W.3d 457, 497 (Tex. 

App.—Fort Worth 2012, pet. ref’d) (“Appellant brought forth no independent affirmative, factual 

evidence—beyond his mere unsuccessful cross-examination arguments—that disputed Butler’s 

testimony.”).

Because there was no disputed fact issue, Cuellar was not entitled to an article 38.23(a) 

jury instruction and, thus, the trial court did not err by refusing to include the instruction. See 

Madden, 242 S.W.3d at 510. 

CONCLUSION

The trial court’s judgment is affirmed.

Rebeca C. Martinez, Justice

DO NOT PUBLISH