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Police forces across the United Kingdom successfully lobbied to deploy a face scanning system known to be biased against females, young people, and members of ethnic minority groups, following complaints that a less biased version generated a reduced number of potential suspects.

How the System Works

UK forces use the national police database to conduct retrospective facial recognition searches. This procedure involves matching a “probe image” of a suspect against a repository of more than 19 million custody photos to find possible hits.

Acknowledged Discrimination

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

“It prompts the question of whether facial recognition only becomes effective if users accept biases in race and sex. Operational ease is a weak argument for disregarding fundamental rights.”

Known Issue

Internal documents show that this discriminatory flaw has been known about for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was intended to address the problem.

Senior officers were informed of the system's bias in September 2024. The Home Office-commissioned NPL review concluded the system was more likely to produce incorrect matches for images depicting women, Black people, and those aged 40 and under.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the accuracy setting required for potential matches be increased to a point where the disparity was greatly diminished.

However, this decision was reversed the next month following complaints from police that the modified technology was producing fewer “investigative leads”. NPCC documents indicate the stricter setting reduced the proportion of searches resulting in potential matches from 56% to a mere under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is currently used, the latest independent review found the system could produce false positives for Black women almost 100 times more frequently than for white women at specific configurations.

The ministry stated on these results: “The testing identified that in a limited set of circumstances the algorithm is has a greater tendency to incorrectly include some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Outlining the effect of the temporary raise to the system's accuracy setting, the police records note: “The change greatly lessens the effect of discrimination across protected characteristics of race, generation and sex but had a significant negative impact on police efficiency”. The documents add that police units complained that “a once effective tactic returned results of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a two-and-a-half-month consultation on its proposals to widen the use of facial recognition technology. Policing minister the relevant minister has described the tool as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the independent scrutiny and oversight board for the national policing equality strategy, commented: “There was scant discussion through race action plan meetings of the facial recognition rollout even with obvious cross-over with the plan’s concerns.

“These revelations show yet again that the anti-racism commitments policing has undertaken via the equality initiative are failing to be integrated into wider practice. Our reports have warned that new technologies are being implemented in a context where ethnic inequalities, inadequate oversight and poor data collection already persist.

“All deployment of facial recognition must adhere to rigorous official guidelines, be independently scrutinised, and prove it reduces rather than exacerbates ethnic bias.”

Home Office Response

A Home Office spokesperson said: “The Home Office treat the conclusions of the study with utmost gravity and we have implemented changes. A updated software has been independently tested and procured, which has no statistically significant bias. It will be trialled in the coming months and will be subject to evaluation.

“Our priority is protecting the public. This gamechanging technology will support officers to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no further action would be pursued without trained officers carefully reviewing the output.”