Five Common Mistakes Made in Forensic Cell Site Analysis

Cory Brodzinski is a Senior Criminal Investigator with the Denver District Attorney's Office. He has 25 years of experience in law enforcement and investigation, extensive experience in cell site analysis, and is a member of the Scientific Working Group on Digital Evidence. Cory is a trainer with one of our US channel partners NW3C , and often shares the lectern with our own founder Joe Hoy.

Introduction 

Forensic cell site analysis has become one of the most common forms of digital evidence presented in modern criminal cases. Nearly all criminal cases involve a phone, a car, or some other device operating on a cellular network. Prosecutors, defense attorneys, investigators, and juries often rely on cellular records to understand where a mobile device, and by extension, potentially its user, may have been at a given time. While these records can be powerful, they also come with limitations. Too often, mistakes are made in interpreting and presenting cell site data, leading to inaccurate conclusions or even the exclusion of evidence in court.  

This paper highlights five common mistakes made in cell site analysis. These include assuming expertise in cell site analysis based solely on experience in mobile device forensics, misunderstanding handoffs, misinterpreting Timing Advance (TA) and specialized historical location data, forcing the data to fit a narrative, and overstating certainty in testimony.

1. Assuming Expertise Based on Mobile Device Forensics 

A growing mistake in the digital forensics community is assuming that expertise in mobile device forensics, computer science, or being a trained network or electrical engineer automatically translates into expertise in cell site analysis. While these fields all may involve cellular devices, they require very different skill sets. Mobile device forensics focuses on data extraction and analysis from the handset itself, such as call logs, text messages, and application data. Cell site analysis, on the other hand, requires knowledge of radio frequency propagation, carrier record formats, and general network engineering. 

Some professionals, confident in their device-level expertise, may testify to call detail records or cell site connections without having the training in this exact discipline to understand the nuances of the underlying records.  This overreach can lead to inaccurate conclusions, expose weaknesses under cross-examination, and damage credibility. 

Courts increasingly recognize that cell site analysis is its own discipline. Analysts must pursue specific training and validation experience in this field rather than assuming expertise by association. Properly distinguishing these areas of forensics protects both the integrity of testimony and the reputation of the expert. 

2. Misunderstanding Handoffs 

Cell phones are designed to maintain service by connecting to the most suitable cell site available. When a device moves or when network conditions change, the phone may “hand off” from one cell site to another. However, this process is not always clean or predictable. 

One common mistake is assuming that each handoff represents physical movement by the device and, therefore, the user. A stationary phone may be handed off due to network management decisions, interference, or load balancing. Conversely, a moving phone may stay connected to one cell site longer than expected because of signal strength, unusual handoff conditions, or the effects of multipath propagation. Practitioners who interpret handoffs too literally risk concluding a device is moving when it is not, or in one location when it may have been somewhere else. 

Thorough analysis requires recognizing that handoffs are influenced by both network engineering and environment. Without corroborating evidence, such as drive test results or other facts of the case, conclusions about movement based solely on handoffs may be speculative. Continual patterns of handoffs to cell sites that are geographically disparate from one another may be more likely to be indicative of device movement than handoffs between cell sites all likely to provide service to the same area.  

3. Misinterpreting Timing Advance Specialized Historical Location Data 

Another major pitfall is over-reliance on Timing Advance (TA) or Round Trip Time (RTT) values. As of this writing, only Verizon Wireless provides records identified as RTT. However, from conversations with Verizon Wireless personnel, what they refer to as RTT is TA. TA is a measure of signal delay, not of distance. From that delay, distance can be inferred. These metrics estimate the distance between a mobile device and a cell site based in part on signal travel time. While they can provide valuable insights, they are not as precise as practitioners may initially think.  

A frequent mistake is treating TA or RTT as equivalent to GPS-level accuracy. Analysts or attorneys may claim that a phone was located at a specific distance or address because of a TA value. These measurements have error margins, possibly hundreds of meters, and are influenced by network conditions, multipath propagation, and equipment configurations. 

Proper use of TA and RTT requires acknowledging their limitations. They should be presented as ranges, not pinpoint locations. If the automated mapping software being used does not allow for this, it should be stated in the analysis report.  

Further, understanding the difference between TA and carrier-specific proprietary point location estimates is critical. These point location estimates may be partly derived from TA, but the algorithms used to calculate them are not shared, so they can't be verified.  AT&T provides this data as LOCDBOR, previously called NELOS. T-Mobile confuses the issue and provides them within the same file as TA (as of this writing). This causes many practitioners to testify that “there are four mappable parts to TA.” There are not. That fourth part they refer to is the point location estimate, which is not TA. Point location estimates are mappable and often come with a radius of uncertainty or confidence interval.  

4. Fitting the Data to the Story Instead of Reviewing It Objectively 

One of the most serious and subtle mistakes in forensic cell site analysis is allowing conclusions to be shaped by a preconceived story rather than objectively examining the evidence. This can occur when an investigator or expert feels pressure to align findings with a prosecution or defense theory, or when confirmation bias creeps in during analysis. 

Instead of starting with an unbiased review of the records, some practitioners begin with the conclusion they want to support and then highlight only the data points that appear to fit. In doing so, contradictory records may be overlooked, mischaracterized, or explained away without adequate justification. This selective interpretation compromises the reliability of the analysis and risks misleading the court. 

Cell site data, like all forms of evidence, must be examined in its entirety and with full acknowledgment of its limitations. A sound methodology involves analyzing the records first, documenting patterns, anomalies, and potential explanations, and only then considering how those findings relate to the broader facts of the case. If the data does not neatly align with a proposed theory, the responsibility of the expert is to report that truthfully, not to force a fit. 

Courts have consistently shown skepticism toward experts whose testimony appears to advocate for one side rather than present an independent technical analysis. By prioritizing objectivity, analysts not only protect their credibility but also ensure that their work serves the justice system rather than undermines it. 

5. Overstating Certainty in Court 

Another, and perhaps most damaging mistake, is overstating certainty when testifying in court. Cell site evidence can provide general insights into the location and movement of a mobile device, but it is not exact. Unfortunately, some experts, whether from overconfidence or under cross-examination pressure, have presented conclusions as more definitive than the data supports. Overstating your knowledge or experience with records is just as dangerous. As of this writing, no data provided by US cellular carriers can provide an exact pinpoint location of a device at a given time.  

Statements such as “the phone was at this house” or “the suspect could not have been anywhere else” - without other supporting evidence - go beyond the science. These overstatements risk misleading juries and can result in exclusion of evidence under Daubert or Frye standards. Creating bad case law is both a disservice to the case at hand and to all practitioners in the field. 

Proper testimony must be balanced, acknowledging both the value and the limitations of cell site analysis. An expert’s credibility depends on honesty about uncertainty. Courts and juries are more likely to accept testimony that is carefully qualified than testimony that appears absolute but unfounded. 

Bonus: How to Avoid these Mistakes in the First Place 

These mistakes are almost entirely avoidable through validation of the records and through peer review of your analysis.  

A peer review is critical and should be expected of any subject matter expert analysis. It is, in fact, a recommended best practice by the Scientific Working Group on Digital Evidence. Have another qualified expert practitioner review your report, any visuals made to support that report and analysis, and your original raw data. They may very well catch problems- both in how you wrote the report and in your train of thought in the analysis- that you missed because you were ‘too close’ to the analysis. Testifying under oath that your analysis has been reviewed also builds credibility with the jury.  

Cellular records can be validated, either through a radio frequency propagation survey (RFPS) or by verifying that cell sites of interest are where the carriers say they are. An RFPS can confirm and validate service areas of identified cell sites of interest. A visual inspection of the cell sites- either in person or, at the very least, finding them in Google Earth or similar programs, can verify they are where the carrier says they are. Both can go a long way to making sure your final analysis is as accurate as possible.  

Conclusion 

Cell site analysis is a powerful tool in modern investigations, but only when applied carefully and responsibly. The most common mistakes- assuming expertise in cell site analysis simply because of expertise in mobile device forensics, misunderstanding handoffs, misinterpreting Timing Advance (TA) and specialized historical location data, making the data fit the story, and overstating certainty in testimony all stem from one root problem: treating cell site data as more precise and straightforward than it really is. 

By avoiding these pitfalls and emphasizing validation, transparency, and specialized knowledge, practitioners can ensure their work withstands scrutiny and provides real value to the justice system. As cellular networks evolve, so must the standards of analysis, always balancing the promise of technology with the responsibility of truthful, defensible testimony. 

Further Reading 

For more on how to avoid these pitfalls, the following references are recommended: 

• Scientific Working Group on Digital Evidence, Recommendations for Cell Site Analysis 17-F-001-2.0 www.swgde.org 

• Scientific Working Group on Digital Evidence, Technical Notes on the Use of Timing Advance Records SWGDE 25-F-002-1.0, www.swgde.org 

• Joseph Hoy, Forensic Radio Survey Techniques for Cell Site Analysis, © 2024 John Wiley & Sons Ltd.