Affirmed and Memorandum Opinion filed November 4, 2021.

In The

Fourteenth Court of Appeals

NO. 14-19-00498-CR

CHARLES MALCOLM ALYEA, Appellant

V.

THE STATE OF TEXAS, Appellee

On Appeal from the 184th District Court

Harris County, Texas

Trial Court Cause No. 1476015

MEMORANDUM OPINION

Appellant Charles Malcolm Alyea appeals his conviction of murder. In one 

issue he contends that the trial court erred in admitting expert testimony regarding 

cell phone tower data. We affirm. 

RELIABILITY OF EXPERT TESTIMONY

In his sole issue appellant argues that the trial court abused its discretion by 

allowing a detective to testify as an expert witness about the location of cellular 

phones based on “call detail records that gave the location of the connected tower.” 
2

Appellant argues that because the detective could not “go beyond the reports 

provided by the cellular companies to explain the results they provided him, the 

State failed to make a clear and convincing showing that the detective’s expert 

conclusions had a reliable foundation. 

A. General Legal Principles

Rule 702 of the Rules of Evidence provides that “[a] witness who is 

qualified as an expert by knowledge, skill, experience, training, or education may 

testify in the form of an opinion or otherwise if the expert’s scientific, technical, or 

other specialized knowledge will help the trier of fact to understand the evidence or 

to determine a fact in issue.” Tex. R. Evid. 702. Before admitting expert 

testimony under Rule 702, the trial court must be satisfied that three conditions are 

met: (1) the witness qualifies as an expert by reason of his knowledge, skill, 

experience, training, or education; (2) the subject matter of the testimony is 

appropriate for expert testimony; and (3) admitting the expert testimony will assist 

the fact finder in deciding the case. Vela v. State, 209 S.W.3d 128, 131 (Tex. 

Crim. App. 2006). These conditions are commonly referred to as (1) qualification, 

(2) reliability, and (3) relevance. Id.

Texas Rule of Evidence 705(c) governs the reliability of expert testimony 

and states that “[a]n expert’s opinion is inadmissible if the underlying facts or data 

do not provide a sufficient basis for the opinion.” Tex. R. Evid. 705(c). The 

reliability inquiry is flexible, at times focusing on the reliability of scientific 

knowledge, at other times on the expert’s personal knowledge and experience.

Vela, 209 S.W.3d at 134. Indeed, experience alone may provide a sufficient basis 

for an expert’s testimony. Id. The proponent of the expert must establish some 

foundation for the reliability of the proffered expert’s opinion. Id.
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To be considered reliable, evidence from a scientific theory must satisfy 

three criteria: “(a) the underlying scientific theory must be valid; (b) the technique 

applying the theory must be valid; and (c) the technique must have been properly 

applied on the occasion in question.” Coble v. State, 330 S.W.3d 253, 273 (Tex. 

Crim. App. 2010) (quoting Kelly v. State, 824 S.W.2d 568, 573 (Tex. Crim. App. 

1992)). When “soft” sciences are at issue, the trial court must inquire “(1) whether 

the field of expertise is a legitimate one, (2) whether the subject matter of the 

expert’s testimony is within the scope of that field, and (3) whether the expert’s 

testimony properly relies upon and/or utilizes the principles involved in the field.” 

Id. (quoting Nenno v. State, 970 S.W.2d 549, 561 (Tex. Crim. App. 1998)). “This 

inquiry is somewhat more flexible than the Kelly factors applicable to Newtonian 

and medical science. Id. The general principles announced in Kelly apply, but the 

specific factors outlined in those cases may, or may not apply depending upon the 

context. Id. Regardless, under both Kelly and Nenno, reliability should be 

evaluated by reference to the standards applicable to the professional field in 

question. Id.

We review a trial court’s decision on whether to allow expert testimony for 

an abuse of discretion. Gallo v. State, 239 S.W.3d 757, 765 (Tex. Crim. App. 

2007). Before reversing the trial court’s decision, we must find the trial court’s 

ruling was so clearly wrong as to lie outside the realm within which reasonable 

people might disagree. See Taylor v. State, 268 S.W.3d 571, 579 (Tex. Crim. App. 

2008); Green v. State, 191 S.W.3d 888, 895 (Tex. App.–Houston [14th Dist.] 2006, 

pet. ref’d). Absent a clear abuse of discretion, the trial court’s decision to admit or

exclude expert testimony will not be disturbed. Wyatt v. State, 23 S.W.3d 18, 27 

(Tex. Crim. App. 2000).
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B. Background 

The State called a detective with the Harris County Sheriff’s Office as an 

expert to testify on the approximate location of appellant’s cell phone before, 

during, and after the murders using appellant’s cell phone records, one of the 

complainant’s cell phone records, and a list of the cell phone towers in the area. 

The trial court conducted a hearing outside the presence of the jury to consider 

appellant’s motion to exclude the detective’s expert testimony. 

At the hearing, the detective testified about his qualifications to opine on

these subjects. He stated that he had been with the Harris County Sheriff’s Office 

for sixteen years and investigating homicides for six years. The detective had sixty 

to seventy credited training hours in “cell phone related investigations” and another

twenty to thirty hours working with another officer in the Houston Police 

Department.

1

 He has also testified in other cases about cell phone mapping and 

that he uses an application of cell phone data in approximately 90% of his cases. 

The detective has looked at hundreds of cases with multiple phones in each case, 

using the cell phone data and “examining it.” The detective testified that he was 

not a “scientist” on cell phone towers and could not go into the “underlying 

theories and why scientists believe that is a good science” behind cell phone tower 

mapping, that he could just read the data produced from the cell phone carriers. 

The detective also testified that the data was “good” because it had been used in 

thousands of courtrooms across the country and supported by the judges in those 

courtrooms. 

The detective testified that he used the calls made in the cell phone records 

to plot distances from the cell towers connected to, to create “sectors” to generally 

1 The officer that the detective worked with was “one of the longest tenured members of

[the Houston Police Department’s] criminal intelligence division who has testified in hundreds of 

trials with regard to cell phone mapping.” 
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estimate where the cell phone is located at the time of the call. He explained that 

multiple phone calls made “eliminates the possibility of being off target. The more 

you have, the more information there is, the easier it is to paint that picture.” In 

this case the detective also used witness statements and surveillance footage to 

confirm that the data provided in the cell phone records was accurately portraying 

the sector plotted from the data. The detective also used additional records, such 

as cell phone records of other persons, to corroborate his findings or show how his 

findings might be faulty. 

When asked whether it was possible that all the calls may have been routed 

to one tower, the detective testified that the calls could not have all been routed to 

one tower because when calls are being routed “off tower,” the records will 

mention that in the report. In addition to compiling the findings into a PowerPoint

presentation, the detective sent his findings to another officer with the Houston 

Police Department for peer review. The detective also provided a report on his 

analysis and findings. The report states that “cell phones constantly monitor their 

environment, continuously communicating with the cellular network and looking 

for the best signal and tower (antenna) to camp on.”

The trial court concluded that the detective’s testimony about the mapping 

done from the cell phone records was admissible and complied with Rule 702 of 

the Rules of Evidence. 

C. Analysis

Appellant argues that the State failed to prove that the conclusions about the 

cell phones’ locations based on cell tower data were reliable, namely that the data 

that was used to compile the reports about the cell phone location was not proved 

to be reliable by the State. Appellant further argues that the detective wrongly 

assumed that cell phones always connect to the closest tower.
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Here, the detective did not simply rely on the information in the reports 

provided by the cellular phone companies, but instead used other information to 

help identify faults or corroborate his findings based on the reports. Appellant’s 

argument is that the detective needs to know the underlying particularities 

regarding how cell phones connect or choose connections to cell towers before 

being able to testify reliably, but as other courts have concluded, this knowledge is 

not relevant to the “relatively simple task” of mapping the general location of the 

cell phone by using towers identified in the call records. See Thompson v. State, 

425 S.W.3d 480, 489 (Tex. App.—Houston [1st Dist.] 2012, pet. ref’d); Robinson 

v. State, 368 S.W.3d 588, 601 (Tex. App.—Austin 2012, pet. ref’d); see also Ward 

v. State, No. 14-15-00473-CR, 2016 WL 6238339, *10 (Tex. App.—Houston [14th 

Dist.] Oct. 25, 2016, pet. ref’d) (mem. op., not designated for publication). 

Appellant argues that the detective could only say with confidence that the 

phone connected to a cell site somewhere within a radius of twenty miles, but 

because of the detective’s assumption that a cell phone would connect to the 

nearest tower the detective’s testimony is “unrealistic and untenable.” Regarding

the allegation that the detective testified that a cell phone always connects to the 

closest tower, the record does not bear this out. The detective testified that he 

reviewed the cell phone records provided by the carriers, in this case AT&T and TMobile, to determine which tower the phones connected to at specific times during 

the relevant dates. Specifically, the detective reviewed records from appellant’s 

phone beginning on April 30, 2015, and ending on May 1, 2015. The detective 

also reviewed records from one of the complainant’s phones beginning on April 

30, 2015, and ending on May 1, 2015. The records themselves show the tower 

connected to by the phone, there was no interpretation involved. The detective 

testified that if a call was being routed “off-tower” that it would be indicated in the 

records provided by the carrier, but that such an indication would not change the 
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location of the phone in relation to the tower. The detective also testified that a 

situation in which every call was routed to one tower would not happen. 

The detective testified that he could “read the data that [the carriers] provide 

so that I can tell you the general location of a cell phone based on the information 

provided and where towers are located.” The detective testified that he could not:

give an exact distance of where the phone is going to be in relation to 

the tower. I can give a sector. What we do is generally estimate 

distances. Distances from the tower to where the phone should be or 

sector ends is a better term or generally estimated from approximately 

one half to two thirds the distance between the towers. Again, that’s 

an estimate.

[I]f all you have is one phone call, you can say, I suppose something 

could have gone haywire there. When you have multiple phone calls, 

that eliminates the possibility of it being off target. The more you 

have, the more information there is, the easier it is to paint that 

picture. 

The detective’s report states that cell phones monitor their environments to look 

for the best signal, not necessarily the closest signal. 

The detective took the data provided by the cellular phone companies and 

placed that data into the “field” by locating each cell site on a mapping program. 

The detective located the cell site from a satellite picture and then from a street 

view picture. The detective then connected the locations of those cell sites to other 

geographic locations of interest in the case, such as the murder scenes, the homes 

of appellant and one of the complainants, the home of other witnesses, the home of

appellant’s parents, and a gas station where appellant purchased lighter fluid. The 

detective also indicated that he checked his results through other evidence he

collected in the case, such as the surveillance video at the Shell station where 

appellant purchased lighter fluid the night of the murders, as well as witness 

statements about where the appellant or one of the complainants were at different 
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times on the night of the murders. Lastly, the detective indicated that his results 

were reviewed by another officer in the Houston Police Department. 

The detective did not testify that the cell phones used by appellant and the 

complainant were necessarily closest to the towers that they connected to, just that 

the towers told him the direction the phones connected from and that it limited the 

location of the phones to a certain geographic sector. For instance, the detective 

testified that between 11:30 p.m. and 11:51 p.m. on April 30, 2015, both the 

appellant and a complainant were “somewhere in the vicinity of Cloverleaf” and 

“somewhere in the vicinity of the eastern portion of Cloverleaf.” The detective 

indicated that, because enough calls were made, he had sufficient information to 

see the “general way they traveled” but couldn’t tell what streets or routes were 

taken. In his analysis, the detective used multiple cell tower connections over 

many hours, which he testified reduced the likelihood of any error. 

Appellant also provides case examples to illustrate how wrongful 

convictions may be obtained from this type of testimony. However, appellant fails 

to detail how the evidence was faulty in the overturned cases or how such 

principles are applicable to the case at hand. For instance, in one of appellant’s 

case examples, Lisa Roberts’s ex-girlfriend was murdered, and her body was found 

in a park. Roberts v. Howton, 13 F. Supp. 3d 1077, 1081 (D. Or. 2014). 

Detectives reviewed Roberts’s cell phone records and found that her phone 

connected to a tower within four miles of the park where the body was found on 

the morning of the murder. Id. at 1086–88. When confronted with this 

information, Roberts’s defense counsel recommended that she plead guilty to the 

lesser charge of manslaughter. Id. at 1101. Roberts accepted the plea. Id. Years 

later upon petition for writ of habeas corpus, the court concluded that her defense 

counsel had rendered ineffective assistance for failing to hire their own expert 

witness to investigate the cell phone records and tower data to put on evidence to 
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refute the prosecutor’s possible expert witness testimony. Id. As part of the writ 

proceeding, in order to show that refuting the conclusions drawn by the 

prosecutor’s expert was possible, Roberts attached expert reports from two experts 

to support her assertion that had her counsel conducted a reasonable investigation

or consulted with an expert, he would have understood the evidence against 

Roberts better and advised her accordingly. Id. at 1102. The court concluded that

counsel’s conduct fell below an objective standard of reasonableness because his 

“assessment of the evidence, and his failure to retain an expert, was not based upon 

a reasonable investigation or understanding of the evidence.” Id. “[T]he 

presentation of expert testimony at trial, concerning the variables impacting the 

reliability of the cell tower evidence to pinpoint the caller’s location, likely would 

have changed the outcome of the trial.” Id. 

In this case, the detective merely offered geographic sectors from the records 

provided.2 The detective did not purport to offer a “pin-point” location of the 

appellant on the dates analyzed. Appellant was permitted to cross-examine the 

detective and highlight that the particular methodology used is subject to

limitations. See Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579, 596 (1993) 

(“Vigorous cross-examination, presentation of contrary evidence, and careful 

instruction on the burden of proof are the traditional and appropriate means of 

attacking shaky but admissible evidence.”). 

Under the circumstances presented herein, based on the testimony of the

detective and how he arrived at his conclusions and that they were supported by 

2 Texas appellate courts have repeatedly classified this type of testimony as non-complex

and relatively “straight-forward.” See Thompson v. State, 425 S.W.3d 480, 488–89 (Tex. App.—

Houston [1st Dist.] 2012, pet. ref’d); Robinson v. State, 368 S.W.3d 588, 599–601 (Tex. App.—

Austin 2012, pet. ref’d); Ward v. State, 14-15-00473-CR, 2016 WL 6238339 (Tex. App.—

Houston [14th Dist.] Oct. 25, 2016, pet. ref’d) (mem. op., not designated for publication);

Patterson v. State, 05-13-00450-CR, 2015 WL 2400809 (Tex. App.—Dallas May 19, 2015, pet. 

ref’d) (not designated for publication).
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other data, such as eyewitness testimony, surveillance footage at the Shell station, 

and camera footage from the homes of witnesses that corroborate the detective’s

expert report, we cannot conclude that the trial court abused its discretion in 

determining the expert’s testimony regarding the location of the cell phones based

on the cell phone records was reliable in this case. See Rhomer v. State, 569 

S.W.3d 664, 672 n.1 (Tex. Crim. App. 2019) (“Reliability is evaluated by looking 

at the method the expert used to come to his conclusions. [The expert’s] testimony 

was reliable because it was based on the information he gathered at the scene: the 

measurements he took, the pictures he captured, the damage he observed, and the 

diagram he created.”); see also William v. State, 606 S.W.3d 48, 56 (Tex. App.—

Houston [1st Dist.] 2020, pet. ref’d) (“The task [the expert] was called upon to 

perform was not complex and it was verifiable. . . . Cell phone records showed the 

exact tower to which the phone connected, and [the expert] testified that she 

checked the records for accuracy. . . . the trial court did not abuse its discretion 

when it determined that [the expert’s] opinion on the general location of . . . the 

phones was reliable.”). 

We overrule appellant’s sole issue on appeal.

CONCLUSION 

Having overruled appellant’s sole issue on appeal, we affirm the judgment

of the trial court. 

/s/ Ken Wise

Justice

Panel consists of Justices Wise, Bourliot, and Spain.

Do Not Publish — TEX. R. APP. P. 47.2(b).