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Police forces across the UK effectively campaigned to use a facial recognition system known to be biased against women, young people, and members of ethnic minority groups, after complaining that a more accurate version produced fewer investigative leads.

How the System Works

British police use the police national database (PND) to carry out searches using historical face recognition. This process entails comparing a “probe image” of a suspect against a repository of more than 19 million custody photos to find potential matches.

Admitted Bias

The UK interior ministry conceded last week that the technology was biased. This acknowledgment followed a review by the government's National Physical Laboratory determined it misidentified Black and Asian people and females at much greater frequency than Caucasian males. The Home Office said it “had acted on the findings”.

“This raises the issue of whether this technology only becomes useful if users accept biases in race and gender. Convenience is a poor argument for disregarding basic freedoms.”

Known Issue

Official papers show that this bias has been known about for more than a year. Furthermore, law enforcement argued to overturn an earlier ruling that was intended to address the problem.

Senior officers were informed of the algorithmic discrimination in late 2024. The Home Office-commissioned laboratory study found the system was more likely to produce false positives for photos of females, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

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

However, this directive was overturned the next month after forces complained that the modified technology was generating fewer “useful lines of inquiry”. NPCC documents indicate the higher threshold cut the proportion of queries that yielded potential matches from over half to a just 14%.

Profound Inequalities

Although the authorities declined to specify what setting is now in operation, the recent NPL study discovered the system could generate incorrect matches for women of Black heritage nearly a hundred times more frequently than for white women at specific configurations.

The Home Office stated on these results: “Our evaluation found that in a specific scenarios the algorithm is has a greater tendency to wrongly flag some demographic groups in its match reports.”

Balancing Utility and Fairness

Describing the impact of the brief increase to the system's confidence threshold, the police records note: “The change greatly lessens the effect of discrimination across legally safeguarded attributes of race, age and gender but had a substantially detrimental effect on operational effectiveness”. The papers further note that forces argued that “a previously useful tool now delivered results of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has launched a ten-week consultation on its plans to widen the use of facial recognition technology. The minister for police Sarah Jones has described the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, head of the advisory panel for the police race action plan, said: “We observed very little discussion in race action plan meetings of the facial recognition rollout despite obvious cross-over with the strategy's goals.

“This disclosure demonstrate once again that the anti-racism commitments the police has made via the equality initiative are not being translated into wider practice. Our reports have warned that new technologies are being rolled out in a context where racial disparities, weak scrutiny and faulty information gathering already persist.

“Any use of this technology must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than exacerbates racial disparity.”

Official Statement

A government representative said: “The Home Office treat the findings of the report seriously and we have implemented changes. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be tested early next year and will be undergo evaluation.

“Our priority is protecting the public. This gamechanging technology will support police to put criminals and rapists behind bars. There is human involvement in every step of the process and no arrest or charge would be pursued without trained officers meticulously examining the results.”