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How Do Police Use Cell Phone Data in Criminal Investigations?

Posted by Ed McClees | May 08, 2019

Every day millions of people use cell phones to send text messages, emails, and to make an occasional phone call. Smart phones help us find directions, check our bank account balances, find good restaurants, and so much more. Smart phones also provide police with a treasure trove of evidence that both state and federal officers use in criminal investigations.


Police often seize a person's cell phone when that person is arrested.  Some people give police officers permission to search their cell phone.  This is a horrible idea unless that person has consulted a lawyer first.  In Riley v. California, 573 U.S. __, 134 S. Ct. 2473, 189 L.Ed. 2d 430 (2014), the United States Supreme Court unanimously ruled that the warrantless search and seizure of the digital contents of a cell phone is unconstitutional.  Therefore, if the person does not give officers person to search his or her phone, the officers will have to obtain a search warrant to search the phone for digital information.

If someone from law enforcement is able to secure a search warrant, police have a variety of methods that they can use to search the cell phone for call logs, voicemails, text messages, emails, and other information.  One rather unsophisticated method is for a police officer to simply open the phone and take photographs of the screen.  This method is forensically unsound and is fraught with problems.  Another method that we commonly see is for officers to use a device manufactured by an Israeli company called Cellebrite.  Law enforcement personnel who are trained in computer and cell phone forensics will attach the phone to this device, and the device will download photographs, videos, text messages, voicemails, emails (sometimes), and other information. There are other more sophisticated methods that are used in unique situations where police are searching for deleted items, or other unique information.


In addition to saving an encyclopedic amount of information about the user, cell phones also leave digital footprints showing where they have been.  Both iPhones and Android based phones have a “frequent locations' feature that will show dates and times that the phone has been at a particular location.  A basic search with the most commonly used Cellebrite devices will not reveal this information, but if the forensic examiner is trained and motivated, there are other methods that he or she can use to find the location information on the phone.

A more common method that police use to find the location of a specific cell phone at a particular time is through information obtained from cell phone towers. A smart phone is constantly communicating with cell phone towers in order to find the strongest signal. The tower that communicates with the cell phone has a limited range.  Therefore, if records show that a specific cell phone was communicating with a specific cell phone tower, then police will know that the cell phone was in the geographical limits of the tower.  This information can place a person's cell phone near the location of a crime or a significant event associated with the crime.  

Federal and state police used to obtain this information with subpoenas.  However, in Carpenter v. United States, 585 U.S. ___, 138 S.Ct. 2206, 201 L.Ed. 2d 507 (2018), the United States Supreme Court held in a 5-4 decision that the government violates the Fourth Amendment by accessing historical records containing the physical locations of cell phones without a search warrant. Therefore, police must now get a search warrant to obtain historical cell phone site information.

Finally, in certain situations federal and state police can use devices such as a Stingray or another device that uses Triggerfish technology to find people in real time.  These devices are most common used to find fugitives.


As a former prosecutor, Ed McClees is well versed in using cell phone historical site information to prove the location of a person's cell phone at a particular time.  He prepared numerous search warrants to enable officers to search cell phones, computers, and other electronic devices for evidence. As a defense lawyer, Ed know that the devil is in the details in these types of cases.  The Texas statute that governs how police can obtain cell phone information is in Texas Code of Criminal Procedure Art. 18.0215 and 18.21.  These statues are convoluted and confusing, and there are many areas where a police officer or a prosecutor can make a mistake that can result in this evidence being inadmissible at trial.

For years, officers were trained to not put certain information regarding cell phone tower searches in their police reports.  Because of this, a defense lawyer who was not trained in these procedures may not even know that this information was used, and may not know where to find it.  If your case involves critical evidence that was obtained from a cell phone or location information from cell phone towers, call Ed McClees.  As the former Chief of the Organized Crime Section at the Harris County District Attorney's Office, Ed knows the finer points of the law on these issues.

About the Author

Ed McClees

Ed is a criminal trial lawyer who is Board Certified in Criminal Law by the Texas Board of Legal Specialization.  He is a former Harris County District Attorney where he served as chief of the Organized Crime Section, prosecuting cases involving complex organized criminal activities, including Fr...

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