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Law enforcement agencies across the United Kingdom effectively campaigned to deploy a face scanning system acknowledged as biased against females, young people, and individuals from ethnic minority groups, following complaints that a more accurate version produced a reduced number of potential suspects.

How the System Works

British police use the national police database to conduct retrospective facial recognition searches. This process involves comparing a “probe image” of a suspect against a repository of more than 19 million mugshots to identify possible hits.

Acknowledged Discrimination

The Home Office admitted last week that the technology was biased. This admission came after a study by the government's National Physical Laboratory determined it incorrectly matched Black and Asian people and women at significantly higher rates than white men. The ministry said it “took steps on the findings”.

“This raises the issue of whether this technology only becomes effective if users tolerate biases in ethnicity and gender. Convenience is a poor argument for overriding fundamental rights.”

Long-Standing Problem

Official papers reveal that this bias has been recognized for over twelve months. Furthermore, police forces lobbied to reverse an earlier ruling that was intended to address the problem.

Police bosses were notified of the algorithmic discrimination in September 2024. The government-ordered NPL review concluded the system was more likely to produce false positives for photos of women, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches be increased to a point where the bias was significantly reduced.

However, this decision was overturned the following month after forces complained that the adjusted system was generating fewer “useful lines of inquiry”. NPCC documents show the higher threshold reduced the proportion of queries resulting in potential matches from 56% to a mere 14%.

Severe Disparities

Although the authorities refused to say what threshold is now in operation, the recent NPL study discovered the system could generate false positives for Black women almost 100 times more often than for white women at specific configurations.

The Home Office stated on these results: “The testing identified that in a limited set of circumstances the algorithm is has a greater tendency to wrongly flag some population segments in its search results.”

Balancing Utility and Fairness

Outlining the effect of the brief increase to the system's accuracy setting, the NPCC documents state: “This adjustment significantly reduces the impact of bias across legally safeguarded attributes of race, generation and sex but had a significant negative impact on police efficiency”. The documents add that police units argued that “a previously useful tool now delivered results of questionable value”.

Broader Rollout Plans

Meanwhile, the government has opened a ten-week public review on its plans to widen the use of biometric scanning systems. Policing minister Sarah Jones has described the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the advisory panel for the national policing equality strategy, said: “We observed scant consideration through equality strategy sessions of the facial recognition rollout even with clear relevance with the strategy's goals.

“This disclosure show yet again that the anti-racism commitments policing has undertaken via the race action plan are not being translated into wider practice. Independent assessments have warned that innovative tools are being rolled out in a context where racial disparities, inadequate oversight and faulty information gathering already persist.

“All deployment of this technology must meet rigorous official guidelines, be subject to external review, and prove it reduces rather than exacerbates ethnic bias.”

Home Office Response

A government representative stated: “We treat the conclusions of the study with utmost gravity and we have already taken action. A updated software has been independently tested and procured, which has demonstrated no measurable discrimination. It will be trialled early next year and will be subject to evaluation.

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