How specific must law enforcement be when seeking a cell phone search warrant? And what must reviewing magistrates and judges consider before authorizing one?

A mobile device, like a cell phone, is a data-rich honeypot of electronically stored information. Unrestricted, an investigative treasure trove can be learned from a device’s:

• Calendars
• Call logs (including participants, timestamps, and duration)
• Chat messages (like Whats App or WeChat)
• Contacts (like email address, phone number, and other saved information)
• Deleted data (like files and text messages)
• Emails (and attachments)
• Ephemeral messaging app info (like Signal, Telegram, or Snapchat)
• File storage (downloaded files, attributes, and metadata)
• Geolocation history or GPS data (like from maps or other app usage)
• Health app activity
• Hidden files (like logs, settings files, or operating system files that are hidden in the user interface to avoid accidental deletion)
• Notes/tasks
• Media files (like photos, screen captures, or videos and their metadata)
• SIM cards (subscriber information modules)
• Text messages (SMS [a text message without an attached file] or MMS [a multimedia text message that includes a file like a photo, video, emoji, or link])
• Third-party app data (like email, productivity tools, social media, and messaging applications)
• Third-party app listing (including installation date)
• Voicemails (including audio files and timestamps)
• Web browser history (and might include browser cache, stored cookies, browser favorites, auto-complete form history, or stored passwords)
• Wi-Fi history (including network names and connection timestamps)

For perspective, the ACLU of Washington has a helpful one-hour video showing and explaining how cell phone data is extracted and searched using a mobile device forensic tool.

In People v Carson, ___ Mich ___ (2025) (Docket No. 166923), the Michigan Supreme Court recently considered whether a criminal search warrant to search a defendant’s cell phone violated the Fourth Amendment’s particularity requirement:

“no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

As part of a larceny in a building and safebreaking criminal investigation, Emmet County Sheriff investigators sought a warrant to search (emphasis added):

1. The person, place or thing to be searched is described as . . .

Cellular device belonging to Michael Georgie Carson . . . .

2. The PROPERTY . . . to be searched for and seized, if found, is specifically described as:

Any and all records or documents* pertaining to the investigation of Larceny in a Building and Safe Breaking. As used above, the term records or documents includes records or documents which were created, modified or stored in electronic or magnetic form and any data, image, or information that is capable of being read or interpreted by a computer. In order to search for any such items, searching agents may seize and search the following: cellular devices; Any physical keys, encryption devices and similar physical items that are necessary to gain access to the cellular device to be searched or are necessary to gain access to the programs, data, applications and information contained on the cellular device(s) to be searched; Any passwords, password files, test keys, encryption codes or other computer codes necessary to access the cellular devices, applications and software to be searched or to convert any data, file or information on the cellular device into a readable form; This shall include thumb print and facial recognition and or digital PIN passwords, electronically stored communications or messages, including any of the items to be found in electronic mail (“email”). Any and all data including text messages, text/picture messages, pictures and videos, address book, any data on the SIM card if applicable, and all records or documents which were created, modified, or stored in electronic or magnetic form and any data, image, or information that is capable of being read or interpreted by a cellular phone or a computer.

The Michigan Court of Appeals and Michigan Supreme Court both found that this cell phone search warrant did not place any limitations on the search’s permissible scope and was not sufficiently particular in the way the Fourth Amendment demands.

Instead, the Supreme Court’s majority opinion found this search warrant’s language to be “a hard-to-decipher amalgamation of seemingly unrelated boilerplate language in one long paragraph.”

The Court found that the fourth sentence’s “any and all data” request wiped out any limiting language suggested by the first sentence.

“We cannot conclude that a practical reading of the search warrant at issue would sufficiently inform an executing officer how to reasonably conduct a limited and constitutionally particular search.” 

“The authorization to search every nook and cranny of the cell-phone data for ‘any and all records or documents’ and ‘any and all data’ related to safebreaking and larceny provides no meaningful constraint in this case.”

Even though the Michigan Supreme Court did not create a per se rule of specificity for cell-phone searches, the Court reminded that “a search warrant should be as particular as the circumstances presented permit and consistent with the nature of the item to be searched.”

For this, the Court explained, “even if the drafter of a search warrant cannot specifically describe the evidence sought, generally an investigating officer will be able to identify a relevant time frame for the criminal activity. Put simply, when information concerning the relevant time frame of the criminal activity exists, this time limitation should be included in the search warrant to ensure adequate particularity.”

As for the data categories to be searched, the Court emphasized the need for the search warrant affidavit to include “the most specific description possible and to support a request to search each category of data mentioned”.

What does it all mean going forward?

In a footnote, the Court explained: Applying such considerations to the facts of this case, the search warrant here might have contained adequate particularity if it had:

• (1) directed law enforcement to search for text messages or communications (categorical limitation),
• (2) between defendant and DeGroff, and
• (3) during August and September 2019 (temporal limitation).

Bottom line: Any mobile device search warrant that seeks “wide-ranging exploratory rummaging is constitutionally intolerable and clearly violates the Fourth Amendment.”

Be particular, in other words. The Fourth Amendment requires it.