In serious crash litigation, one of the first decisions an attorney makes about Call Detail Records (CDRs) is how wide to set the time window. Too narrow, and you risk missing the activity that matters. Too wide, and the production becomes unwieldy, the records that count get buried in the noise, and the defense has a ready objection.
Recently, I posted a poll on LinkedIn asking exactly that question: How wide should the critical window be around a crash? The four answers ranged from minutes around impact to days or weeks as a baseline. There is no single right answer. The right window depends on what you are trying to show, what the carrier is likely to have retained, and what you already know about the facts.
That distinction matters in personal injury and commercial motor vehicle (CMV) cases because the window shapes everything downstream: the subpoena language, the production, the analysis, and the opinion. Set it wrong before the records arrive, and you may not find out until discovery is closed.
Option 1: Minutes Right Around Impact
When This Is True
A narrow window centered on the crash time makes sense when the facts of impact are already well-established and the only remaining question is whether the driver was on the phone at that precise moment. If a witness places a call in progress at impact, or if surveillance footage brackets the time closely, a short window may be sufficient for that specific, narrow question.
What the Records Can Support
CDRs can show voice calls, text messages, and data sessions within that window. If a call was connected at or within a minute of impact, the record will typically show a start time, a duration, and the direction of the call. A text or Multimedia Messaging Service (MMS) entry in that band provides a timestamp. Data session entries show a period of network activity, though they do not establish what the driver was doing on the phone.
Limits and Pitfalls
This approach carries real risk. A narrow window assumes you already know when the crash happened down to the minute and that the carrier’s timestamps are aligned to the correct time zone. Coordinated Universal Time (UTC) offsets and clock drift can shift entries by several hours or minutes. When there is any uncertainty about the precise crash time, build in margin.
More importantly, a narrow window gives you no context. You cannot tell from a two-minute slice whether the driver’s phone use was a routine habit or an isolated moment. You also cannot see what happened in the lead-up to the crash, which is often where the more revealing activity sits.
A note from practice. Not long ago, I worked on a case where both sides agreed to limit the records request to one hour before and one hour after the crash. It seemed reasonable. The records that came back showed no voice or text activity in that window, only data usage. That result raised more questions than it answered.
As the case developed, we suspected something was off with the device extraction the other side produced. We went back and subpoenaed a broader set of carrier records. The expanded production showed voice calls in the carrier’s records that were absent from the device extraction. The discrepancy put the integrity of the device evidence directly in question. That development contributed to a more favorable settlement.
The lesson is not that narrow windows are always wrong. A narrow window, agreed to before the analysis is done, can close off the very context you need. Involving a qualified cell phone records expert before you negotiate the scope of a subpoena is one way to avoid that problem. The expert can assess what is likely to exist, identify what could be missed, and help frame a request that fits the facts rather than one that fits the calendar.
Option 2: The 30 to 60 Minutes Before
When This Is True
In most distracted driving cases, the 30 to 60 minutes before impact is where meaningful analysis begins. A single call at the moment of the crash may establish phone use, but a pattern of calls, texts, and data activity in the lead-up shows something more. It can support a picture of sustained inattention rather than a single lapse.
What the Records Can Support
CDRs in this window can show whether the driver was in a sustained conversation, was exchanging texts with another party, or had a data session open. Taken together, those entries build a record of phone engagement that extends beyond a single moment. In commercial vehicle crash litigation, this window often captures dispatcher communications that raise separate questions about fleet management and supervision.
Limits and Pitfalls
This window still omits the post-crash period. Calls made immediately after a crash can be just as significant as calls made before it. Who the driver called, in what order, and how quickly those calls were made can all bear on the facts and on whether the driver understood what had happened. A window that closes at impact leaves that evidence uncollected. In commercial vehicle crash cases, post-crash communications between a driver and a company representative can be particularly relevant, and carrier records are often the only independent source for those contacts.
Option 3: The Whole Trip, Start to Impact
When This Is True
In commercial vehicle crash litigation where driver fatigue, hours-of-service (HOS) compliance, or a pattern of distraction is at issue, the full trip window makes the most sense. If the driver started a shift eight or ten hours before the crash, phone activity across that entire period may be relevant. CDRs can show whether the driver was making calls during periods when he should have been resting or whether phone use was a recurring pattern throughout the trip.
What the Records Can Support
A full-trip production provides the most complete picture of phone behavior during the period that matters. Paired with Electronic Logging Device (ELD) data, driver logs, or dispatch records, CDR entries from across the trip can help corroborate or challenge a driver’s account of his schedule and rest periods. In cases where fatigue is contested, the overlap between phone activity timestamps and required off-duty time can be particularly telling.
Limits and Pitfalls
A broader request requires a proportionality argument, and the defense will object without one. You will need to connect the scope of the request to the specific claims in the case. A full-trip window also produces more records, and more records require more careful analysis. Finding the critical entry in a large production is harder, and carrier-specific formatting differences make that work more complicated than it looks. A records expert who is familiar with how different carriers structure their productions can significantly reduce the time it takes to locate what matters.
Option 4: Days or Weeks as a Baseline
When This Is True
A baseline window, covering days or weeks before the crash, serves a different purpose than the other three. It is not primarily about finding the critical entry near the crash. It is about establishing what normal phone use looked like for this driver, so the crash-window activity can be evaluated in context.
What the Records Can Support
A baseline production can support impeachment if the driver claims he never uses his phone while driving, but the records show consistent call activity during operating hours across multiple days. It can also reveal patterns, such as regular dispatcher contact during freight runs, that give context to the entries closest to the crash.
Limits and Pitfalls
Baseline requests face the most resistance in discovery. Without a clear factual basis, courts may find them overbroad. The request must be targeted and justified. A baseline request that is not grounded in specific allegations is unlikely to survive challenge.
An Illustrative Framework: Pre-Crash, Crash, and Post-Crash
The graphic below shows a practical way to think about the three phases of a CDR time window. Each phase serves a different analytical purpose, and collapsing them into a single narrow band around impact often means missing at least one.
The pre-crash window supports questions about pattern, distraction, and the driver’s state before impact. The crash window supports questions about phone use at the moment of impact. The post-crash window supports questions about who was contacted, how quickly, and in what order. A well-constructed records request collects all three.
Tips for Attorneys
- Set the window before you negotiate the subpoena. Agreeing to a narrow scope before you have reviewed any records can eliminate evidence you didn’t know you needed. Do the preliminary work first, or have an expert do it.
- Build in margin around the crash time. Carrier timestamps are not always in local time. A buffer of at least five or six hours (depending on time zone) on each side of the known crash time protects against UTC offsets and clock drift.
- Request post-crash records, not just pre-crash. Calls made in the minutes after impact can be significant. Do not let the window close at the moment of the crash.
- Consider the purpose before setting the width. A narrow window answers a narrow question. A broader window answers questions about pattern and baseline. Know which question you are asking before you file the subpoena.
- Pair CDRs with other records before finalizing scope. ELD data, dispatch logs, witness statements, and surveillance footage can help verify whether the window you are considering captures what it needs to.
- Involve a qualified cell phone records expert before you agree to a records scope. Carrier productions vary in format, field names, and completeness, and it is difficult to identify a gap in a production without knowing what that carrier normally provides. An expert can review the scope of the request before it is filed, not after the records arrive.
- Preserve broadly and narrow analytically. Where the rules allow, request a wider window and focus the analysis on what the facts support. It is easier to set aside records you do not need than to go back for records that are gone.
Conclusion
There is no default answer to how wide the critical window
should be. Each of the four poll options is correct in the right case, and the
mistake is treating any one of them as a starting point rather than a
conclusion.
The narrow window works when the facts are already tight and
well-documented. The pre-crash window works when pattern and lead-up behavior
are at issue. The full-trip window works in fatigue and hours of service cases.
The baseline window works when impeachment or habit is part of the theory.
A practical approach is to identify what you are trying to
show, work backward to the window that would capture it, and then build in
enough margin to account for timestamp variation and gaps in the production.
Set the scope before negotiating it, and revisit it if the first production
raises new questions, as it often does.
Closing Note
CDRs are easy to misread, and the scope of the subpoena is
one of the earliest points where a records analysis can go wrong. A qualified
expert is an integral part of setting that scope correctly, reviewing the
production for completeness, and interpreting the records accurately before
depositions or preservation windows close.
Ben Bierce of Brave Investigations works with civil
litigation attorneys on call detail record analysis and carrier record review
in Texas and nationally. He can be reached at ben@braveinvestigations.com
or through the contact form at braveinvestigations.com. Texas Department of Public Safety
license number A28412101.