Geofence Warrants

The government may request that a court issue a 'geofence warrant'. This is a warrant which gives law enforcement authorities the right to obtain data from any cell phones which were in the same vicinity where a crime took place. A reverse location search is performed by a service provider to disclose all device identifiers picked up in a certain geographic radius in a particular time range. Some courts have ruled that these warrants are not constitutional.

GPS and CSLI Data

Note the difference between global positioning system (GPS) and cell site location information (CSLI). Both can be used to track the position of a mobile device, but they involve different techniques.

A GPS system uses radio waves sent from a satellite to a receiver inside the phone. The transmission need only go from the satellite to the phone, not vice versa. The system needs signals from four satellites to triangulate the phone's position. The GPS system should be able to determine location to within 10 feet.

A CSLI system uses information from cell phone towers in the immediate vicinity to pin down the location of the phone.

A AGPS (assisted global positioning system) uses cellular data to assist the GPS system to ascertain location. AGPS is actually less precise than GPS, but it uses less power.

The Sixth Circuit distinguished between GPS data and CSLI data in United States v. Carpenter, concluding that there was no search and no warrant was required because cell site location information is data used to facilitate communications, and the information could be obtained from a service provider rather than the individual's device itself. See, United States v. Carpenter, 819 F. 3d 880 (6th Cir. 2016).

The Supreme Court reversed the Sixth Circuit finding that, “[I]n fact, historical cell-site records present even greater privacy concerns than the GPS monitoring considered in Jones: They give the Government near perfect surveillance and allow it to travel back in time to retrace a person’s whereabouts, subject only to the five-year retention policies of most wireless carriers. The Government contends that CSLI data is less precise than GPS information, but it thought the data accurate enough here to highlight it during closing argument in Carpenter’s trial. At any rate, the rule the Court adopts ‘must take account of more sophisticated systems that are already in use or in development,’ and the accuracy of CSLI is rapidly approaching GPS-level precision.” United States v. Carpenter, 138 S. Ct. 2206, 2210 (2018) (citation omitted).

Is your text message a SMS message?

SMS messages are often regarded as being synonymous with text messages, but actually there are several different types of text messages.

OTT (over the top) messages are sent via the internet - no carrier is necessary - a message can be sent on the web, or using an app. WhatsApp and Facebook Messenger are widely used OTT messaging apps. SMS (short message service) systems use a cellular network connection It's not necessary to have a smartphone to send a SMS message. Mobile phones use the SMPP (short message peer-to-peer protocol) whenever a SMS message is sent. OTT messaging apps use various internet protocols such as RTSP (Real Time Streaming Protocol). WhatsApp uses the Extensible Messaging and Presence Protocol (XMPP)

A SMS text message system will not require access to other apps, or the mic and camera of a smartphone as OTT apps often do. SMS messaging is more likely to be subject to government regulations restricting SPAM.

A SMS text message is limited to 160 characters. Many mobile phones use MMS (multimedia messaging service) to send text messages which allows for a larger number of characters, and also photos, videos, and audio which could not be sent in a SMS message. MMS is based on SMS technology. Often MMS messages will be limited to 300 KB - 600 KB. Such limitations will not apply to OTT messages.

The IMessage app on an Apple iPhone sends texts via Apple's servers. They differ from standard SMS messages in that they use end-to-end encryption. An iMessage text can be sent via a cellular network if internet access is not available.