The United States Supreme Court ruled that police can continue to use cell phone location data to identify criminal suspects, as long as they obtain judicial authorization and respect specific limits. The decision was made in the case Chatrie v. United States and represents one of the most important recent definitions of digital privacy and criminal investigation.
How does this method work in practice?
Imagine that a bank is robbed at 2 pm.
Investigators don’t know who the criminal is, but they know exactly where and when the crime happened.
Instead of asking for information about a specific person, the police ask the court for a geofence warrant, authorizing Google to search which cell phones were in that region at that time.
The procedure typically takes place in three steps:
Anonymous device list
Google sends a list of all cell phones that were within the given area, but without revealing who the users are. Each device only receives a numeric code.
Filtering
The police analyze the paths of these devices. Anyone who just passed quickly down the street can be discarded. A cell phone that remained at the scene of the robbery before, during and after the crime is now attracting attention.
Investigators can then ask Google for additional information about just those specific devices, without revealing the owners’ identities.
Identification
Only when there is sufficient evidence do the police request user data — such as name and Google account — from devices considered relevant to the investigation.
It was exactly this procedure that led to the identification of Okello Chatrie, convicted of the robbery investigated in the case.
The ministers understood that this type of investigation does not violate the Fourth Amendment of the Constitution, as long as there is judicial authorization and the request is limited to a specific area and period of time.
In practice, the Court concluded that the police can use this technology to find suspects when they do not yet know who they are.
Privacy experts warn that a warrant of this type could include hundreds of innocent people who were just in the area of the crime — customers of a business, residents or pedestrians.
Prosecutors and police say that the tool has become essential for solving crimes in which there are no witnesses or suspects identified.
With the Supreme Court’s decision, the use of so-called geofence warrants remains authorized in the United States, consolidating an important precedent on the use of cell phone location data in criminal investigations.
