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Police forces across the United Kingdom successfully lobbied to deploy a facial recognition system acknowledged as biased against females, young people, and members of ethnic minority groups, after complaining that a less biased version generated fewer investigative leads.

How the System Works

British police utilize the national police database to conduct retrospective facial recognition searches. This process entails matching a “probe image” of a suspect against a database of over 19 million custody photos to identify potential matches.

Acknowledged Discrimination

The Home Office admitted last week that the technology was flawed. This acknowledgment followed a review by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and women at much greater frequency than Caucasian males. The ministry stated it “had acted on the findings”.

“It prompts the issue of whether this technology only becomes effective if users accept discrimination in ethnicity and sex. Convenience is a weak argument for disregarding fundamental rights.”

Long-Standing Problem

Internal documents reveal that this bias has been recognized for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was intended to address the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned NPL review concluded the system was more likely to suggest false positives for images depicting women, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In response, the national police leadership body mandated that the confidence threshold required for potential matches be raised to a level where the disparity was greatly diminished.

However, this decision was reversed the following month following complaints from police that the adjusted system was generating a lower number of “useful lines of inquiry”. NPCC documents indicate the higher threshold reduced the number of searches resulting in potential matches from over half to a mere 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is currently used, the recent independent review found the system could produce incorrect matches for women of Black heritage almost 100 times more frequently than for Caucasian women at specific configurations.

The Home Office commented on these findings: “Our evaluation identified that in a specific scenarios the software is more likely to incorrectly include some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the impact of the temporary raise to the system's accuracy setting, the police records state: “The change greatly lessens the effect of discrimination across protected characteristics of ethnicity, age and gender but had a substantially detrimental effect on operational effectiveness”. The documents further note that police units complained that “a previously useful tool now delivered outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week consultation on its plans to expand the use of facial recognition technology. Policing minister Sarah Jones has described the technology as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the advisory panel for the national policing equality strategy, said: “There was very little discussion through race action plan meetings of the technology deployment despite clear relevance with the strategy's goals.

“These revelations demonstrate once again that the anti-racism commitments the police has made via the equality initiative are failing to be integrated into broader operations. Independent assessments have cautioned that innovative tools are being rolled out in a context where racial disparities, inadequate oversight and poor data collection continue to exist.

“All deployment of this technology must meet strict national standards, be independently scrutinised, and prove it reduces rather than exacerbates ethnic bias.”

Home Office Response

A government representative said: “The Home Office takes the findings of the report with utmost gravity and we have already taken action. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be trialled early next year and will be subject to evaluation.

“The foremost aim is protecting the public. This gamechanging technology will assist police to apprehend and prosecute offenders. There is human involvement in each stage of the process and no arrest or charge would be pursued without specialist personnel carefully reviewing the results.”