Facial Recognition Technology

Facial Recognition (FR) technology can be used in a number of ways by the Met, including to prevent and detect crime, find wanted criminals, safeguard vulnerable people, and to protect people from harm – all to keep the people we serve safe.

Whilst the Met’s documents you can find linked from this page give you a lot more detail about the terms we use as well as how and where FR is used by the Met. The typical uses of FR technology for policing are:

• as a real-time aid to help officers to help them locate people on a ‘watchlist’ who are sought by the police;
• as an operator initiated tool for officers who decide they need to take an image of a person and then use Facial Recognition software to help them establish who that person is. This helps the police even if that person provides false or misleading details. This use of FR can also help provide an identification of someone who is unconscious or seriously injured and unable to communicate who they are;
• as a retrospective system to be used after an event to help officers establish who a person is or whether their image matches against other media held on databases.

Live Facial Recognition

LFR cameras are focused on a specific area; when people pass through that area their images are streamed directly to the Live Facial Recognition system.

This system contains a watchlist: a list of offenders wanted by the police and/or the courts, or those who pose a risk of harm to themselves or others. Further details of who can be on a watchlist and how the Met carefully decides where to use LFR can be found in our Standard Operating Procedures for LFR.

LFR is not a ubiquitous tool that uses lots of CCTV cameras from across London to track every person’s movements. It is a carefully deployed overt policing tactic to help locate a limited number of people the police need to find in order to keep London safe.

Should you have questions about personal data, you can email the Met data office. Or, you can write to the data controller at:
c/o MPS Data Office
PO Box 313
Sidcup
DA15 0HH

Or see the Met Privacy Notice for more information. 

Testing of Facial Recognition Technology

Why we tested

The Metropolitan Police Service (the Met) and South Wales Police (SWP) tested Facial Recognition Technology (FRT) with the National Physical Laboratory (NPL). The NPL is a world-leading centre of excellence that provides cutting-edge measurement in science, engineering and technology.

Thanks to previous testing by the National Institute of Standards and Technology (NIST) the Met and SWP knew that their FRT used a high performing algorithm. The aim of the testing was to develop an in-depth understanding of the performance of the algorithms when it was being used in an operational environments. The three policing use cases were:

• Live Facial Recognition (LFR)
• Retrospective Facial Recognition (RFR)
• Operator Initiated Facial Recognition (OIFR)

The NPL test plan was specifically designed to help identify any impact this technology may have on any protected characteristics, in particular race, age and sex.

What the test results tell us about the algorithm

The NPL report gives us an impartial, scientifically underpinned and evidence-based analysis of the performance of the facial recognition algorithm currently used by the Met and SWP. It tells us:

• we now better understand the demographic performance of our LFR system. There are settings our algorithm can be operated at where there is no statistical significance between demographic performances.
• that there was no demographic performance variation for RFR
• that there was no demographic performance variation for OIFR

The results from the tests help the Met and SWP with further understanding of how to use FRT fairly in order to prevent and detect crime, safeguard national security and keep people safe.

The full results are presented in the NPL’s commissioned report: ‘Facial Recognition Technology in Law Enforcement Equitability Study’

The PDF(s) on this page may not be suitable for users of assistive technology. We are in the process of updating them, but please email us to request an accessible version. See our accessibility statement.

Retrospective Facial Recognition

The Met has now completed the initial implementation of its new Retrospective Facial Recognition (RFR) system.

In order to realise the benefits of being able to use this technology earlier the Met has chosen to use the system as a Minimum Viable Product (MVP). This means for a period of time the system will have a small number of reduced capabilities and functions. An example of this is, for a period of time, only being able to search against some of the custody image database.

This approach means RFR will now be available to help with investigations and incidents post event where there is still imagery or a short video of an unknown person(s) of interest.

The images or short videos that are being searched in this system are typically obtained from CCTV, mobile phone footage or have been supplied by members of the public. Those images can then be searched against some of our custody image database. If the system indicates a match then a human will always review this and they will decide if they think it is a match or not.

Details of how we use RFR can be found in our RFR Policy document.

Operator Initiated Facial Recognition

The Met keeps its need to use Facial Recognition technologies under review but does not presently use Operator Initiated Facial Recognition. Further details about Operator Initiated Facial Recognition can be found in the Met’s Live Facial Recognition Policy document where we set out the different types of Facial Recognition technology and how we refer to them.