If you are going to claim an alibi defense (i.e., I was somewhere else), one piece of evidence we can use might be your cell phone data.

Because your phone “pings” off cell phone towers, data retained by your cell phone provider may show where your phone is located (it does not necessarily show you were with your phone, however).

Phone location data comes in two forms:

• Active data (call detail records — CDR): CDRs are only generated when a phone “does something”—placing a call, sending a text, or initiating a background data exchange.
• Passive data (cell site location information — CSLI): If a phone is sitting silently in a pocket, it generates CSLI (passive network pings)

Significance of CDR vs. CSLI data:

• If we have CDR/Active data that means someone is with the phone and doing something; if it is something you’d likely do (vs. a friend — e.g., a call or text to your Mom) this could show you were with your phone at that time.
• Because there is so much CSLI/passive data (collected even when you are doing nothing), carriers delete this data much faster to clear server space.
  • This is most clear for AT&T below. They appear to keep CDR data for 5 to 7 years; but only keep CSLI data for 13-24 months.

Bottom line: If you have an alibi defense, the sooner your attorney gets these phone records the better.

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Below is a breakdown of data retention policies for the three major U.S. mobile carriers, highlighting both short-term tracking and long-term historical records:

Carrier	Call Detail Records (CDRs) (Long-Term / Active)	Cell Site Location Information (CSLI) (Short-Term / Passive)	Notes & Technical Caveats
AT&T	5 to 7 years	13 to 24 months	AT&T holds the longest archive of CDRs. To pull location data past 2 years, the target device must have active triggers (calls, SMS, or data sessions).
T-Mobile (Includes legacy Sprint)	2 years	Up to 24 months	T-Mobile keeps both active and passive location data synchronized to a standard rolling 2-year window.
Verizon	1 year	1 year	Verizon has the tightest retention window. Passive pings and CDR tower logs are purged after 12 months. Immediate preservation letters are critical.

Key Distinctions for Alibi Defense Posts

The “Tower Key” Necessity: Subpoenaing the records is only half the battle. Carriers return data as raw spreadsheets listing alphanumeric tower sector IDs. Legal teams must explicitly request the Cell Site Tower Keys / Azimuths to map those IDs to actual physical addresses.