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Police forces across the United Kingdom effectively campaigned to use a face scanning system known to be biased against females, youths, and individuals from ethnic minority groups, following complaints that a more accurate version generated a reduced number of investigative leads.

The Technology in Practice

British police use the police national database (PND) to conduct retrospective facial recognition searches. This procedure involves comparing a “probe image” of a suspect against a database of over 19 million mugshots to identify potential matches.

Acknowledged Discrimination

The UK interior ministry admitted last week that the technology was biased. This admission came after a study by the National Physical Laboratory (NPL) determined it misidentified people of Black and Asian heritage and females at much greater frequency than white men. The ministry stated it “had acted on the findings”.

“This raises the question of whether this technology only becomes useful if users accept discrimination in ethnicity and gender. Operational ease is a weak argument for overriding fundamental rights.”

Long-Standing Problem

Internal documents reveal that this bias has been recognized for more than a year. Furthermore, police forces lobbied to reverse an initial decision that was intended to mitigate the problem.

Police bosses were informed of the system's bias in September 2024. The Home Office-commissioned NPL review concluded the system was more likely to produce false positives for photos of females, Black people, and those under 40 years old.

A Policy U-Turn

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

However, this directive was reversed the following month after forces complained that the adjusted system was producing fewer “investigative leads”. NPCC documents show the stricter setting reduced the proportion of searches that yielded potential matches from over half to a mere 14%.

Profound Inequalities

Although the Home Office and NPCC declined to specify what threshold is now in operation, the recent NPL study 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 ministry stated on these findings: “Our evaluation found that in a limited set of circumstances the software is has a greater tendency to wrongly flag some population segments in its match reports.”

Balancing Utility and Fairness

Describing the impact of the temporary raise to the system's accuracy setting, the NPCC documents note: “This adjustment significantly reduces the effect of bias across legally safeguarded attributes of race, generation and sex but had a significant negative impact on operational effectiveness”. The documents further note that police units complained that “a once effective tactic now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a two-and-a-half-month 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 genetic fingerprinting”.

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 scant discussion through race action plan meetings of the facial recognition rollout even with clear relevance with the plan’s concerns.

“This disclosure show yet 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 warned that innovative tools are being implemented in a context where racial disparities, weak scrutiny and faulty information gathering already persist.

“All deployment of facial recognition must adhere to strict national standards, be subject to external review, and prove it diminishes rather than exacerbates racial disparity.”

Home Office Response

A Home Office spokesperson said: “The Home Office takes the findings of the study seriously and we have already taken action. A updated software has been independently tested and acquired, which has no statistically significant bias. It will be tested in the coming months and will be undergo evaluation.

“Our priority is ensuring public safety. 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 arrest or charge would be taken without trained officers meticulously examining the results.”