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Cell phone data can be the critical piece of evidence in a car collision that helps prove who was at fault.As a personal injury attorney in Cincinnati there have been multiple times that allegations were made that my client, the injured party, or the defendant tortfeasor, the individual we claim was at fault, have been accused of talking or texting on their cell phone at the time of the accident.

Gathering and interpreting cell phone record evidence almost certainly requires an expert in the area of preserving and interpreting cell phone evidence. As an attorney handling car accidents, I try to make expert witness connections that I can go to for credible and reliable information about cell phone forensics and other digital or technological evidence.  Recently, I came across such an expert, Benjamin Bierce.  He has all the credentials to be an expert in the area of cell phone record gathering, analysis and mobile device forensics.

I asked him if he would help educate myself and other lawyers about this very nuanced area.  Although common place, this evidence is also extremely technical.  Mr. Bierce was gracious enough to write this excellent article on cell phone forensics that I am elated to share for the first time as a public service.


Cell phone saturation is almost complete. According to a 2017 Pew Research Center study, 95% of Americans own cell phones. When dealing with auto accident cases, there was likely at least one cell phone in each of the vehicles involved. The phone company records associated with these cell phones can contain information extremely valuable to cases in civil litigation. Even if the phone was destroyed in the crash, the phone company will likely still have the records. In one case I worked on, the cell phone records alone made a half-million-dollar difference in the settlement.

Types of Records

Cell phone companies keep two basic types of records; Call Detail Records (CDR) and billing records. The CDR contains information such as the calling phone number, the receiving phone number, the time and date of a call to the second, the duration of a call to the second, and the first and last cell sites used by the phone during a call. Some companies include text messages and data connections in the CDR while other companies provide this information in separate documents. The information available varies by company.

Billing records usually only contain calls with the time a call was placed to the minute and the duration to the minute. If the records show a call started at 7:04 PM the call could have started between 7:04 PM and zero seconds, to 7:04 PM and 59 seconds. If the records show a call lasted five minutes the call could have lasted four minutes and one second to five minutes and zero seconds.  That means the end of the call can only be determined within a one minute, 58 second window. Two minutes can make a significant difference when determining whether or not a phone was active at the time of a crash. This is one reason it is important to obtain CDR’s rather than billing records.

Time Companies Keep Records

Phone companies are subject to 18 USC §2703, which requires the companies to maintain their records for 180 days. Most companies will maintain records CDR’s for a year or more, but they will likely keep the billing records longer. Here’s how long the major companies keep their CDR records with cell site information:

  • AT&T – Everything back to July, 2008
  • Sprint – 18 to 24 months
  • T-Mobile – 24 months
  • Verizon – 12 months

Cell site information would likely be important in most cases. Therefore, it’s critical to preserve the CDR even if a case hasn’t yet been filed in court. Phone companies are required to preserve the records for an additional 90 days upon request. Preservation requests may be sent every 90 days until a case is filed which could potentially go on for years. Once the case is filed the defense can obtain a court order or a subpoena for the CDR.
The Legal Demand

The Legal Demand

As of this writing AT&T and Verizon will honor a third-party subpoena for the CDR, but Sprint and T-Mobile require a court order signed by a judge. Recent revelations regarding the National Security Agency’s collection of cell phone records have brought privacy concerns to the forefront of public attention. Likely the phone companies will tend to be more restrictive in releasing phone records, and AT&T and Verizon may change their policies to require a court order to obtain the records. A court order is always the safest way to go.

Another reason to obtain the records through a court order is the turnaround time. Most phone companies have separate sections to respond to subpoenas and court orders. The subpoena sections handle much higher volumes than court order/search warrant sections. Subpoenas may take a month or more to return the records while court orders take weeks or days. The extra time and effort it takes to get a court order will likely pay off in getting the records more quickly.

Additional Information

An experienced analyst can determine whether or not a party’s phone was in use at the time of the crash. But, the analyst needs more information than just what’s available in the records. The time of the crash is usually determined by the time of the first call to 911. Therefore, the analyst needs additional information such as the 911 center call recordings and the Computer Aided Dispatch (CAD) records. These records may need to be obtained from more than one agency.

For example, if a crash occurs on the interstate, it usually falls under the jurisdiction of the state police or highway patrol. However, most calls to 911 are routed to the county or city 911 dispatch center. Once a dispatcher at the county or city center learns the crash is on the interstate, the call is forwarded to the state police or highway patrol dispatch center. Obtaining the county or city CAD report and 911 recordings can help the analyst determine the earliest possible time of the crash even if the state police or highway patrol submitted the report.

The police report and crash report will help the analyst determine the location of the crash. A police report and crash report may be different for the same crash. Most states have standardized crash reports, but, especially in a crash involving serious injury or death, the reporting agency may generate a local report in addition to the crash report. Deposition transcripts of the plaintiff and witnesses will also be valuable to the analyst. The analyst can determine if statements are consistent or inconsistent with the information found in the phone records.

Test Calls

All this information may not be enough. There may be a deviation between the time listed on the phone records and the timestamp of the 911 call recordings and the time on the CAD report. For example, if the phone records show the phone call ended at 7:04 PM and 15 seconds, and the timestamp for the 911 center recording of the first 911 call shows 7:06 PM and 20 seconds, it would appear the first 911 call occurred two minutes and five seconds after the end of the call.

However, the analyst can determine the deviation between the cell records time and the 911 center time by making test calls to 911 with a phone on the same network as the phone in question. The analyst will go to the area of the crash to ensure the same cell site is accessed. The records for the test calls are then preserved and obtained in the same way as the plaintiff’s phone records were obtained, and the analyst can obtain the 911 recordings and CAD reports for the test calls.

Once the analyst has the records for the test calls they can be compared to the timestamp on the 911 recordings and the CAD report to determine the deviation between the phone company and the 911 center. This deviation can then be applied to the phone records and compared to the 911 center times to determine if the phone was on an active call during the time of the crash.

For example, if the analyst found the deviation from the cell phone company to the 911 center was plus two minutes and 30 seconds, the end of the call on the 911 center timeline would be 7:06 PM and 45 seconds, which would mean the call in question ended 25 seconds after the first 911 call. In the best case one of the phones that called 911 would be on the same network as the phone in question. In this case the records for the 911 caller can be obtained and there would be no need to make test calls. This can also apply to text messages and, sometimes, data connections.

Cell Sites

Cell site information can also be useful. Cell sites are often referred to as cell towers or towers. While most cell sites are towers, many cell sites have the antennas attached to other pre-existing structures such as buildings, water towers, or power line structures. Some cell sites are designed to look like other things such as trees or flag poles.

An analyst can use the CDR to map the cell sites used by the phone and determine if the call in question was using a cell site consistent or inconsistent with the phone being at the crash scene. For example, if one of the parties stated in a deposition that he or she was not on the phone at the time of the crash, and the call in question began and ended at home. If the home is several miles from the crash scene, and the call ended on the cell site closest to the crash scene, then deposition statement is inconsistent with the records, but consistent with the phone being on an active call at the crash scene.

If a party’s home was close to the crash scene, and likely covered by the same cell site, the sectors may be able to tell whether the phone was more likely in use at the home or the crash scene. Most cell sites, especially ones in urban areas, are sectored cell sites. These cell sites have three sectors facing out from the center. Each sector is comprised of a set of directional antennas. The standard coverage area for each sector would be 120°. The cell site would cover 360°, divided by three sectors would be 120° for each sector. Not all cell sites are set up like this.

If the home is clearly in one sector, and the crash scene was clearly in another sector, and the records showed the phone using the sector covering the crash scene, the records would be clearly inconsistent with the deposition statement that he or she was home at the time of the call. The records would also be consistent with the party’s phone being used during the time of the crash.


The time shown on the records may not correspond with other times in the case.  If too much time has passed to make reliable test calls, and none of the 911 callers were on the same network as the party in question, no correlation between the 911 center time and the phone record time can be established. The analyst’s conclusion as to whether or not the phone was in use will be less precise.

Cell phone record analysis cannot show the exact location of a phone. The records show the cell site or sites used by the phone around a certain time. Generally speaking, a phone will connect with the strongest signal, which is usually, but not always, the closest tower.

One reason a phone might not connect with the closest tower is terrain. If there is a substantial hill or mountain obstructing line of sight between the closest cell site antennas and the cell phone, the phone will likely connect with a cell site farther away, but with no obstructions.

Another reason a phone might not connect with the closest tower is referred to as load leveling. Cell sites have a limited capacity. Once a particular cell site is receiving significantly increased usage compared to neighboring cell sites, calls to the particular cell site will be routed to other cell sites in range. Imagine the cell towers around an NFL stadium. Most days the cell sites surround the stadium will connect with the cell phones of users who live or work in the area. On game days, the demand on the cell sites surrounding the stadium will obviously increase. The cell phones that normally connect with the cell sites surrounding the stadium would be routed to cell sites farther from the stadium.


To make the most of cell phone records action should start as soon as possible after an accident, preferably the day of the accident. Test calls are most reliable when made shortly after an accident. Preservation requests should be sent immediately upon the identification of a significant phone number, and subsequent preservation requests should be sent for that number until the records can be obtained through a court order.

While cell phone record analysis has certain limitations, it can be powerful evidence to support other information in a case.


Mobile Fact Sheet, Pew Research Center, January, 2017, retrieved September 23, 2017 from

About Bierce

Benjamin Bierce is the founder and owner of Bierce Associates LLC ( Bierce Associates provides litigation support services in the form of cell phone record analysis and mobile device forensics. Bierce is also a detective with the Franklin (IN) Police department, a former detective with the Indianapolis Metropolitan Police Department where he served in the Homicide, Robbery and the Computer and Digital Forensics Unit. Bierce is also a retired Special Agent with the US Army Criminal Investigation Division (CID). Bierce has analyzed over 1200 sets of phone records and testified in 28 trails as an expert witness. Bierce may be reached at [email protected] or 317-527-1446.

About Anthony Castelli

Antony Castelli is a personal injury attorney in Cincinnati, Ohio with over 30 years of experience helping accident victims harmed my the negligence of others get fair compenastion. Call for a free claim consultation at 513-621-2345