The Race Against the Clock

In a case that turns on where a phone was, or who it was talking to, the single biggest factor is rarely the expert you hire or the motion you file. It is whether the records still exist when the subpoena arrives. Cellular carriers do not keep everything forever, and the data points with the most evidentiary value tend to be the ones with the shortest shelf lives. Attorneys who wait a few weeks to send a preservation letter often find that the most useful records are already gone.

What Actually Disappears, and When

Retention varies by carrier, by record type, and sometimes by the customer's plan. The carriers themselves disclosed their retention windows to the FCC in 2022.¹ T-Mobile retains precise latitude and longitude data for roughly 90 days, with less granular cell site data held for up to two years. Verizon retains cell site data for approximately one year. AT&T holds cell site records considerably longer, in some cases up to five years.

A more granular breakdown from forensic practitioners shows where the real bottlenecks are. Verizon's Range to Tower (RTT) data, which gives the most precise distance estimates, is typically kept only about 8 days. Tower dumps are held for roughly one year. SMS content sits on Verizon's systems for 3 to 5 days. AT&T retains RTT data for around 180 days but does not store SMS content. T-Mobile also does not retain text content.

The takeaway is straightforward. The fields attorneys care most about—precise location estimates, message content, and short-term network event data—are exactly the ones the carriers delete first. Standard call detail records and basic tower connection logs survive much longer, but the granular evidence that wins suppression motions and proves alibis often has a retention window measured in days.

Two Different Tools for Two Different Lawyers

Attorneys often use the phrase "preservation letter" loosely, but the mechanism is not the same in every context. The distinction matters because using the wrong one can leave a litigant with no enforceable hold on the records.

The 2703(f) Letter (Government Only)

Under 18 U.S.C. § 2703(f),² a governmental entity can send a written request directing a provider of wire or electronic communication services to preserve records and other evidence in its possession. The statute requires the provider to retain those records for 90 days, with a single 90-day renewal available on request. Law enforcement uses these routinely, and its model letter expressly covers both metadata and content.

A 2703(f) letter does not compel disclosure. It is a hold. The government still has to come back with a warrant, a 2703(d) order, or a subpoena to actually obtain the preserved material.

The Civil Preservation Letter

Section 2703(f) is not available to civil litigants. A plaintiff or defendant who wants to preserve a third party's cell records relies on a different mechanism: a common law preservation letter combined with a prompt third-party subpoena. The letter puts the carrier on notice that the records are relevant to pending or anticipated litigation. The subpoena is what actually compels production.

Carriers are not legally obligated to honor a private preservation request the way they must respond to a 2703(f) letter. They will often hold records as a matter of practice, but the practical safeguard for civil counsel is speed.

What to Ask For

A preservation request or subpoena should be specific about the data fields requested, the time window, and the target number or device identifier. Generic requests for "all phone records" produce billing statements that omit the technical fields needed for any meaningful location analysis. At a minimum, the request should cover the following:

• Call detail records (CDRs) covering voice, SMS, and data sessions, including originating and terminating numbers, start and end times, duration, and the cell tower and sector identifiers used for each event.
• Per Call Measurement Data (PCMD) where the carrier collects it, particularly for Sprint and T-Mobile legacy networks.
• NELOS data for AT&T accounts — AT&T's proprietary Network Event Location System, which uses internal algorithms to estimate device location.
• Timing Advance and Range to Tower (RTT) values where available. These are short-retention fields and need to be flagged immediately.
• Tower lists, sector azimuths, and beam widths for every tower that appears in the records. Without this geographic reference data, the CDR cell IDs cannot be mapped.
• SMS and MMS content where retained, with the understanding that most carriers do not hold message content beyond a few days.
• Subscriber information, including account holder, billing address, plan type, and any associated devices or IMEIs.

Counsel should also request preservation of any internal network event databases that go beyond the standard CDR set. Some carriers maintain supplementary location databases that are not produced unless specifically named.

Common Mistakes That Cost Attorneys the Evidence

• Sending a preservation letter without following up with legal process. Preservation is temporary. Without a warrant, court order, or subpoena, the carrier eventually purges the held data.
• Requesting "phone records" instead of CDRs with cell site data. Billing records and CDRs are different products. Billing records will not contain the tower information needed for location work.
• Waiting for charging decisions or for a civil complaint to be filed. The retention clock starts running at the date of the event, not at the date of the lawsuit. By the time the case is captioned, RTT data and message content may already be gone.
• Failing to preserve the device itself. Carrier records show the network's view of activity. The device contains its own location artifacts, including GPS history, Wi-Fi association logs, and app-based location data. Many of these have no carrier equivalent.
• Assuming the records can be re-requested later. Once the carrier's retention window closes, the data is gone. There is no archive.

A Realistic Timeline

For a serious incident with cellular evidence, the practical timeline looks something like this:

• Within 24 to 72 hours: identify the relevant numbers, devices, and time windows. Send preservation letters to every carrier involved. Government counsel sends 2703(f) letters; civil counsel sends common law preservation letters.
• Within the first week: identify and preserve the physical devices through a forensic image. Engage an examiner who can perform a proper extraction and chain of custody documentation.
• Within the first 30 days: serve subpoenas, warrants, or 2703(d) orders to actually obtain the held records. Confirm receipt with the carrier's legal compliance group and verify that what arrived matches what was requested.
• Renew preservation requests as needed. The initial 2703(f) hold runs for 90 days, but a single renewal is permitted, and civil counsel should send updated letters whenever the production timeline slips.

Why This Matters for the Outcome

Early preservation is so often decisive because cell site evidence is rarely produced in a vacuum. A defense expert who can show that the prosecution's mapping is overstated needs the underlying tower lists and timing data to do it. A plaintiff trying to prove a driver was texting at the moment of impact needs CDR fields that show data session activity to the second. A geofence challenge depends on the full set of records the carrier produced to law enforcement.

In every one of those scenarios, the analysis depends on data the carrier may have already deleted. If a case involves a cell phone, the question of preservation belongs at the first client meeting, not at the first motion deadline. A short preservation letter takes minutes to send. The records it protects can take years to litigate.

---