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Law enforcement agencies across the UK effectively campaigned to deploy a facial recognition system acknowledged as discriminatory against females, young people, and members of ethnic minority groups, following complaints that a less biased version produced fewer potential suspects.

How the System Works

UK forces use the police national database (PND) to conduct searches using historical face recognition. This process involves matching a “probe image” of a suspect against a database of more than 19 million custody photos to identify potential matches.

Admitted Bias

The UK interior ministry conceded last week that the system was biased. This admission 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 Home Office said it “took steps on the findings”.

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

Known Issue

Internal documents show that this bias has been recognized for over twelve months. Furthermore, police forces lobbied to reverse an earlier ruling that was designed to mitigate the problem.

Senior officers were notified of the system's bias in September 2024. The Home Office-commissioned NPL review found the system was had a higher probability to produce false positives for photos of females, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) mandated that the accuracy setting required for possible hits be raised to a point where the bias was significantly reduced.

However, this directive was overturned the next month following complaints from police that the modified technology was generating a lower number of “investigative leads”. Internal records show the stricter setting reduced the number of searches that yielded potential matches from over half to a mere 14%.

Profound Inequalities

Although the authorities declined to specify what threshold is currently used, the recent independent review discovered the system could produce incorrect matches for women of Black heritage almost 100 times more frequently than for white women at certain settings.

The Home Office stated on these findings: “The testing found that in a limited set of circumstances the software is has a greater tendency to incorrectly include some demographic groups in its search results.”

Balancing Utility and Fairness

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

Wider Implementation Proposals

Meanwhile, the government has launched a ten-week consultation on its proposals to widen the use of biometric scanning systems. Policing minister Sarah Jones has described the technology as the “most significant advance since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the advisory panel for the police race action plan, commented: “There was scant consideration in race action plan meetings of the technology deployment even with clear relevance with the strategy's goals.

“This disclosure show yet again that the anti-racism commitments policing has made via the race action plan are not being translated into broader operations. Our reports have warned that new technologies are being implemented in a landscape where racial disparities, weak scrutiny and poor data collection continue to exist.

“All deployment of facial recognition 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 study with utmost gravity and we have implemented changes. A updated software has been externally evaluated and acquired, which has no statistically significant bias. It will be trialled early next year and will be subject to evaluation.

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