Cellular Site Simulator
The Los Angeles County Sheriff’s Department (LASD) is committed to ensuring public safety and enhancing our ability to serve and protect our community. As part of this mission, the Department has acquired a Cellular Site Simulator (CSS), an advanced tool designed to assist in law enforcement investigations while prioritizing transparency and accountability.
Department Policy
It is the policy of the LASD to respect the privacy and civil liberties of individuals and to follow the U.S. Constitution, particularly the First and Fourth Amendments, the California Constitution and all applicable laws.
For more information about California Law and Department Policy, please see:
California Government Code § 53166(b) – Link
County Approval of Cell Site Simulator Purchase – PDF
LASD Homicide Bureau Order Number 4-9 – PDF
How The Technology Works
Cellular site (also known as cell site) simulator technology relies on the use of cellular site simulators. Cellular site simulators function by simulating a cell tower. In response to the signals emitted by the simulator, cellular devices in proximity to the simulator identify it as the most attractive cell tower in the area and thus transmit signals to the simulator that identifies the devices in the same way that they would be by a regular networked cell tower.
A cellular site simulator receives signals and uses an industry-standard unique identifying number assigned by a device manufacturer or cellular network provider to distinguish between the incoming signals until the targeted device is located. Authorized department members who are trained in the use of cellular site simulator technology can use the cellular site simulator to help locate cellular devices whose unique identifiers are already known to law enforcement, or to determine the unique identifiers of an unknown device by collecting limited signaling information from the devices in the simulator’s vicinity. Once the cellular site simulator identifies the specific cellular device for which it is searching, it will obtain the signaling information relating only to that particular device, rejecting all others.
CSS Use/Search Warrants
Absent exigent circumstances, a search warrant signed by a judicial officer is required before the cellular site simulator can be operated by the LASD. This judicial oversight ensures that usage of the cellular site simulator meets the legal threshold for the U.S. Constitution and the Constitution of the State of California.
Incidents involving an exigent circumstance, such as a kidnapping, report of a missing child, mass casualty incident, natural disaster, or evidence of a criminal act that could lead to imminent death or infliction of serious bodily injury are the exceptions to the requirement for immediately obtaining a search warrant prior to operation of the device. After the exigent circumstance has passed, LASD will submit a search warrant for judicial review, no later than 72 hours after use of the cellular site simulator for this purpose.
With respect to an unknown device, once law enforcement discovers the unique identifiers of an unknown device, investigators are required to obtain a subsequent search warrant to allow them to gather additional information relevant to that unique identifier.
Law Enforcement Investigative Uses of CSS
Cellular site simulator technology may be used to gather information leading to the identity or whereabouts of missing persons, at-risk individuals, victims of mass casualty incidents, suspects, and fugitives.
When used with respect to a mass casualty incident, the cellular site simulator will obtain signaling information from all devices in the simulator’s target vicinity for the limited purpose of locating persons in need of assistance or to further recovery efforts. Any information received from the cellular devices during this time will only be used for these limited purposes and all such information received will be purged at the conclusion of the effort in accordance with LASD policy. A mass casualty incident is a natural disaster such as an earthquake or fire; a terrorist attack; or any event resulting in imminent loss of life or injury.
The cellular site simulator shall not be used to target First Amendment activities, such as protests and gatherings at places of worship. The cellular site simulator also shall not be used for immigration enforcement purposes, such as the sharing of information derived from the equipment with federal immigration authorities including Immigrations and Customs Enforcement (ICE) and Customs and Border Patrol (CBP).
Privacy Issues
Cellular site simulator technology does not capture nor receive any content such as text messages, voicemails, applications, multimedia messages, etc. It does not have the capability of listening to phone calls. The LASD will not add software or otherwise modify the equipment in any way to enable such capacities.
Cooperation/Sharing of Information with Other Law Enforcement Agencies
The LASD will share information gathered through the use of cellular site simulator technology with other law enforcement agencies in accordance with a lawful investigative purpose and a court order, search warrant, or identified exigency on the part of the agency.
The LASD will not share information outside of the legal parameters necessary for the lawful investigative purpose. All requests for information shall be reviewed by the Homicide Bureau Captain.
The law enforcement agency with which the information is shared (“recipient agency”) shall be designated as the custodian of such information. The recipient agency shall be responsible for observance of all conditions of the use of the information including the prevention of unauthorized use, retention of information and destruction of information.
The acquisition of this tool reflects our dedication to leveraging technology to enhance public safety while respecting the constitutional and privacy rights of all individuals. LASD is mindful of the importance of balancing effective law enforcement, public safety, and individual privacy rights.