Cell Phone Expert Witness
Cellular records show up in more cases than most attorneys expect, and this evidence is misread more often than most attorneys realize. I analyze cell phone data, cell tower records, and cellular carrier records to tell you what the evidence actually supports, and how much uncertainty comes with it.
I’m Mark McFarland, a licensed Professional Engineer with a graduate degree in telecommunications engineering and over 30 years working directly with cellular and wireless systems. This is one of the practice areas I get the most calls for, and one of the areas I’m most frequently retained on across both civil and criminal matters. If your case turns on where a phone was, when, or what the carrier’s records show, speak with a licensed engineer who has extensive training, experience, and knowledge in cellular evidence.
What I Analyze
Cell Tower and Carrier Records
I review Call Detail Records (CDRs) and cell site data to determine what location and movement information the records genuinely support, and just as importantly, what they don’t. A device connecting to a tower narrows its likely location to a coverage area; it very rarely pinpoints an exact spot, no matter how confidently a report presents it that way.
Mobile Device Usage Data
Voice, SMS, and data usage patterns are often central to timing and activity questions, particularly in cases involving whether someone was using a phone at a specific moment. This evidence is often used to determine whether a motorist was texting at the time of an accident.
Where This Evidence Commonly Gets Misread
Cell tower data can show that a device was connected, through a switch, to one of several plausible towers at a given time. A single confirmed location is often not available. In practice, I’ve seen analyses tailored to select the tower that best fits a preferred narrative and stop there. Analysts sometimes lack a full understanding of how cellular communication networks work, and as a result are unable to account for every tower a device could realistically have used. I map and analyze records from every major carrier and device manufacturer, and I present the uncertainty in the data honestly, including where a location conclusion is strong and where it’s genuinely ambiguous. I provide thorough analysis and clear explanations for the court.
Discuss Your Case
Fifteen minutes covers the engineering question, any conflicts, and whether my background fits. No charge, no obligation.
Cellular Tower Analysis in Criminal Appeals
Cellular tower evidence has become a routine part of criminal trials, and increasingly, a routine basis for appeals. When the original cellular analysis in a case didn’t account for every plausible tower a device could have used, or treated an uncertain location conclusion as a certain one, that gap can become the central issue on appeal.
I’ve provided cellular tower analysis in multiple criminal appeal matters. I reviewed whether the original trial-level analysis correctly accounted for the physical and technical limitations of the underlying cellular network and its records. My findings are explained and referenced clearly enough for an appellate court to understand exactly where the original analysis went wrong.
How Cell Tower Location Analysis Is Supposed to Work
A cell phone connects to the tower that provides the strongest usable signal at a given moment, which is not always the nearest tower. Depending on terrain, network congestion, antenna sector orientation, and a range of other factors, a device in a given location could plausibly connect to any of several nearby towers. The records may indicate details such as which switch, tower, and sector the device connected to; some records include GPS coordinates, distance, and angle from the tower.
Sector and Antenna Orientation
Cell towers typically use directional antennas covering specific sectors, not a full 360-degree radius. An analysis that ignores sector orientation, or misattributes which sector a connection used, can place a device in entirely the wrong part of a tower’s coverage area.
Why This Matters More on Appeal Than at Trial
At trial, a jury often hears cellular tower testimony presented with more confidence than the underlying data supports, and without a defense expert available or retained to challenge the methodology. On appeal, that gap becomes reviewable: was the original analysis technically sound, and did it accurately represent the level of certainty the data could support? I approach these cases by independently analyzing the underlying records and provide defensible opinions based on scientific and engineering principles, as well as industry and forensic best practices.
My Process
- Initial call. You describe what the case needs, and I tell you directly whether cellular analysis is likely to help.
- Records review. Once retained, I review the available carrier records or platform logs.
- Mapping and analysis. I build out the location and timeline picture the data actually supports, tower by tower, data point by data point.
- Ongoing communication. You hear what I’m finding as I go, including if the data doesn’t support the theory of the case.
- Report and testimony. If the findings support your position, I prepare a report clear enough for a judge or jury to follow without a technical background, and I’m available for deposition and trial testimony nationwide.
My Process for Appellate Cellular Tower Review
- Record acquisition. Reviewing the underlying carrier records and any tower location data referenced in the original trial testimony.
- Independent tower mapping. Identifying every tower the device could plausibly have used at the relevant time, not just the one cited in the original analysis.
- Methodology comparison. Evaluating whether the original analysis’s conclusions are supported by the full set of technical possibilities, or whether it relied on an incomplete picture.
- Credentials review. Evaluating the credentials of the original testifying expert. Individuals sometimes testify as experts without substantive training, skill, experience, or knowledge in the relevant field.
- Report and testimony. A written opinion suitable for appellate briefing, and testimony where the matter requires it.
Why Attorneys Retain Me for Cellular Cases
- One of my most requested practice areas, with deep, current experience across carriers, device types, and case types.
- I’ve never had an opinion limited or excluded. No Daubert challenge has ever succeeded against me, including in appellate criminal matters where the stakes for getting the analysis right are the highest.
- I work both plaintiff and defense, which keeps my analysis grounded in what the data shows rather than what one side needs it to show.
- Nationwide licensure. My NCEES Engineering Record lets me take on cases outside Colorado or California without a licensing delay in most jurisdictions.
- Trusted appellate experience. I have been retained on several criminal cases through state-funded indigent defense programs, providing reports, affidavits, and testimony for individuals unable to afford an expert in matters where state law requires the appointment of one.
FAQs
It depends. Carrier records show which tower a device connected to, which usually narrows a location to a coverage area rather than a single point. Sometimes the records can provide more precise location information. It’s important to have these records examined by an engineer who understands the design and operation of cellular networks.
Rarely with the level of certainty it’s sometimes presented with. A tower connection narrows a location to a coverage area, which can span several square miles depending on terrain and tower configuration. Certainty beyond that generally requires additional corroborating evidence.
Typically, a showing that the original trial-level analysis didn’t account for the full range of towers a device could plausibly have used, or overstated the precision the data actually supports. That gap has to be demonstrable through an independent, rigorous re-analysis of the underlying records.
Both. My cellular practice covers trial-level analysis and appellate review, since the technical questions and the standard of review differ meaningfully between the two settings.
It depends on the volume of records and the complexity of the tower network involved, but I generally need at least a month of lead time to complete a thorough, defensible analysis.
Talk to Mark About Your Case
Cellular evidence can make or break a case, but only if it’s read correctly the first time. If your matter involves cellular data, at trial or on appeal, I’d welcome a direct conversation about what the records can and can’t tell you.