How Call Detail Records (CDR) Analysis Can Reveal the Truth in Vehicle Accident Cases

In personal injury litigation involving vehicle accidents, one of the most critical questions is often: Was the driver using their cell phone at the time of the collision? Call Detail Records (CDR) obtained from cellular carriers can provide powerful forensic evidence to answer that question — but only if they're properly interpreted.

In a recent case involving a vehicle accident in Southeast Texas, our firm was retained to analyze AT&T Call Detail Records belonging to a defendant driver. The opposing side's forensic consultant — a certified digital forensics examiner with multiple Cellebrite certifications and a GIAC Advanced Smartphone Forensics credential — had submitted a sworn declaration concluding that the driver was multitasking on their phone while in motion at the time of the accident. Upon closer examination, that conclusion turned out to be based on a fundamental misunderstanding of how AT&T CDR records and emergency network infrastructure actually work.

This case offers important lessons for attorneys, forensic examiners, and anyone involved in accident litigation about the dangers of surface-level CDR interpretation.

What Are Call Detail Records?

Call Detail Records are a complete and detailed log of transactions between a cellular device and the carrier's network. They document activities such as incoming and outgoing calls, voicemail, text messaging, and location-based information derived from cell tower connections.

There are several important things to understand about CDRs. They are not accessible to the customer and can only be obtained directly from the carrier via subpoena or search warrant. Their timestamps are recorded to the second, making them highly precise. They are considered a technical document suitable for expert analysis. And unlike data on the device itself, CDR transactional history cannot be deleted by the user.

One critical detail that trips up many analysts: AT&T CDR timestamps are recorded in UTC (Universal Coordinated Time) and must be properly converted to the local time zone for accurate analysis.

Tracking a Device's Location Throughout the Day

Using Cell Hawk Analysis software — a widely recognized forensic tool used by over 300 law enforcement agencies whose methodologies are based on the FBI's CAST Team recommendations and SWGDE standards — we loaded the carrier's CDR records and mapped the device's location history for the entire day of the accident.

This analysis allowed us to track the device's movements across multiple cities throughout the day, from the driver's home in the early morning hours, through several work locations during the day, and ultimately to the site of the accident in the late afternoon. This type of timeline reconstruction is invaluable in accident cases because it can corroborate or contradict a driver's account of their whereabouts, establish travel patterns, and identify the approximate time a driver arrived at the accident location.

The Opposing Expert's Conclusions: A Case Study in Misinterpretation

To understand why proper CDR interpretation matters, it's worth examining exactly what the opposing expert concluded in their sworn declaration.

The opposing expert identified four specific CDR record entries near the time of the accident and drew the following conclusions from them:

Voice record #1 showed the device attempted to contact a 10-digit local phone number at 3:55:44 PM, which the expert stated was "physically dialed" or accessed via a contact link.

Voice record #2 showed the device dialed 911 at 3:55:57 PM — thirteen seconds later — lasting 2 minutes and 12 seconds.

Data record #1 occurred at the same timestamp as voice record #1 (3:55:44 PM). The opposing expert interpreted this as "simultaneous call and data usage" that was "indicative of phone multitasking." They also noted two different cell location values, concluding the phone was "in motion" during this activity.

Data record #2 occurred five seconds later at 3:55:49 PM with a single cell location value, which the expert interpreted as the phone being "no longer in motion."

The opposing expert's sworn conclusion was that the driver dialed a phone number while data activity was occurring, indicating device multitasking while in motion, the phone then stopped moving, and nine seconds later 911 was dialed. The implication was clear: the driver was actively using their phone while the vehicle was in motion at the time of the accident.

This interpretation was wrong on multiple levels.

What Actually Happened: The SOS APN Network

The opposing expert's fundamental error was failing to understand AT&T's emergency network infrastructure — specifically, the SOS APN (Access Point Name).

An APN is a set of settings a device uses to connect to a carrier's network. The SOS APN is a specialized emergency access point that must be present in all networks according to 3GPP (3rd Generation Partnership Project) standards — the global technical specifications that govern how mobile networks operate. When the SOS APN is triggered, it ensures the highest priority on the network, giving emergency calls pre-emption over non-emergency calls and data sessions.

Here's what the CDR records actually showed when properly interpreted:

The 10-digit phone number the opposing expert identified as a separate call was, in fact, a local 911 dispatch center line number. Research confirmed this number belongs to a Community Support and Referral Services number associated with emergency dispatch. Critically, this call entry showed no CSLI (Cell Site Location Information) connection and no seizure time — meaning it never actually connected as an independent phone call.

The data records the opposing expert cited as evidence of "multitasking" were actually the device connecting to the AT&T SOS APN emergency network. The CDR data records confirm the AT&T APN SOS connection times at 3:55:44 PM and 3:55:49 PM — the exact same timestamps as the voice records. This is not a coincidence; it's the normal technical process of a 911 call being routed through the emergency network.

When a person dials 911 on AT&T's network, the CDR captures multiple entries that are all part of a single emergency call event: the 10-digit phone number assigned to the dispatch call center (without CSLI), the SOS APN network data connections facilitating the emergency routing, and the 911 call itself (with CSLI). The 911 call center has multiple lines assigned to it, which correspond to various numbers designated for the call center to receive incoming calls.

It was essentially one call — a 911 call — not two calls made "simultaneously" with concurrent data activity indicating multitasking.

Where the Opposing Expert Went Wrong

The opposing expert made several specific analytical errors worth highlighting for other forensic professionals:

Confusing emergency network data activity with user-initiated data usage. The data records occurring at the same timestamp as the voice records weren't evidence of the driver browsing the web or using apps while making a call. They were the SOS APN facilitating the emergency call — a standard carrier network function that happens automatically when 911 is dialed.

Misidentifying a dispatch center number as a separate phone call. The 10-digit number was not a call the driver independently placed. It was a routing artifact of the 911 call appearing in the CDR records. The absence of CSLI data and seizure time on this entry should have been a red flag that this was not a standard connected call.

Interpreting cell tower changes as evidence of motion during phone use. Two different cell location values in the data record don't necessarily mean the driver was using their phone while driving. They reflect the SOS APN network handoff during the emergency call routing — a process that involves the network, not the user.

Drawing conclusions about user behavior from network-level activity. Perhaps most importantly, the opposing expert conflated what the network was doing (routing an emergency call) with what the user was doing (allegedly multitasking on the phone). This is a critical distinction in CDR analysis that requires understanding carrier-specific network architecture.

The Data Usage Question

Separately from the 911 call records, the CDR revealed a data transaction lasting approximately 14 minutes and 42 seconds on the device, occurring at roughly 3:45 PM on the AT&T "Nxtgenphone" APN — the standard LTE data connection. The total data transferred was modest: approximately 0.09 MB uploaded and 0.39 MB downloaded.

This is where intellectual honesty in forensic analysis becomes critical. Based solely on CDR data usage records, an examiner cannot determine whether the data usage was passive or interactive (background app refresh vs. active browsing), what type of data or applications were in use, which applications were launched on the device, or whether the user was actively engaging with the device at all.

Modern smartphones generate constant background data traffic — push notifications, email sync, location services, app updates, and system processes all create data records in the CDR without any user interaction whatsoever. Any speculation about the type of usage without a full forensic extraction and analysis of the actual device using specialized forensic software is exactly that — speculation.

Corroborating Evidence: The Full Picture

Our analysis didn't rely solely on CDR interpretation. We cross-referenced multiple independent data sources, and they all told a consistent story.

The Texas Peace Officer's Crash Report estimated the accident occurred at approximately 3:56 PM. The Fire and EMS Dispatch Report logged the initial emergency call at 3:56:46 PM. The Law Enforcement Communications Report logged an initial call at 3:56:35 PM. And the driver's deposition testimony stated they were not talking on the phone at the time of the accident.

The CDR records, properly interpreted, show the device's 911 call beginning at 3:55:57 PM — consistent with the driver calling for emergency assistance immediately after (or during) the incident, not making a personal call before or during the accident. The slight timing variations between the CDR timestamp and the dispatch logs are normal and expected, as they reflect different systems recording the same event.

Lessons for Attorneys and Forensic Professionals

This case highlights several critical takeaways:

Certifications alone don't guarantee correct CDR interpretation. The opposing expert held multiple respected forensic certifications. However, CDR analysis requires specialized knowledge of carrier-specific network architecture — including understanding APNs, emergency network routing, and how different record types interact — that goes beyond mobile device forensic extraction skills. Knowing how to image and analyze a phone is a different skill set than interpreting the carrier's network transaction logs.

Always verify the opposing expert's methodology. In this case, the opposing expert's declaration presented conclusions that appeared technically sound on the surface. It took a deeper understanding of AT&T's SOS APN infrastructure to identify that the entire analysis was built on a flawed premise. Attorneys should always consider retaining an independent CDR expert to review opposing declarations.

CDR records are technical documents — not self-explanatory spreadsheets. Carrier record formats vary significantly between AT&T, T-Mobile, and Verizon. Each carrier provides a records key document that defines its fields and terminology. An examiner who doesn't thoroughly understand the carrier's specific documentation, network architecture, and APN types can easily reach incorrect conclusions.

Not all data usage equals distracted driving. Modern smartphones generate constant background data traffic. Without a forensic examination of the device itself, CDR data usage records alone cannot establish that a driver was actively using their phone.

Cross-reference multiple independent sources. Crash reports, dispatch logs, CDR records, and deposition testimony should all be compared. When they align, as they did in this case, the conclusion is far more defensible than relying on a single data source.

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Computer Forensic Services, Inc. (CFSI) is a veteran-owned digital forensics firm headquartered in Dallas, Texas, serving the legal community since 1997. We provide expert analysis of Call Detail Records, mobile device forensics, computer forensics, and expert witness testimony in state and federal courts. For more information, visit cfsiusa.com or call 214-498-5666.

This blog post was AI-assisted in its drafting and is based on actual casework and expert analysis by Lance Sloves.