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Police forces across the UK successfully lobbied to use a facial recognition system known to be biased against females, young people, and individuals from minority ethnic backgrounds, following complaints that a more accurate version generated fewer investigative leads.

The Technology in Practice

British police use the national police database to conduct searches using historical face recognition. This procedure involves comparing a reference photograph of a person of interest against a database of over 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office conceded last week that the system was flawed. This acknowledgment followed a study by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and women at significantly higher rates than Caucasian males. The Home Office said it “had acted on the findings”.

“It prompts the issue of whether this technology only becomes effective if users tolerate biases in ethnicity and sex. Convenience is a poor argument for overriding basic freedoms.”

Long-Standing Problem

Official papers show that this bias has been known about for over twelve months. Furthermore, law enforcement argued to overturn an earlier ruling that was intended to mitigate the problem.

Senior officers were notified of the system's bias in September 2024. The Home Office-commissioned laboratory study concluded the system was more likely to produce false positives for photos of females, 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 raised to a point where the disparity was greatly diminished.

However, this directive was reversed the next month after forces complained that the adjusted system was generating a lower number of “useful lines of inquiry”. NPCC documents show the stricter setting cut the number of searches that yielded possible identifications from over half to a mere under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is now in operation, the latest NPL study discovered the system could generate false positives for women of Black heritage nearly a hundred times more frequently than for Caucasian women at specific configurations.

The Home Office stated on these results: “Our evaluation found that in a limited set of circumstances the software is more likely to incorrectly include some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Outlining the effect of the temporary raise to the system's confidence threshold, the NPCC documents state: “The change significantly reduces the impact of bias across protected characteristics of ethnicity, generation and sex but had a substantially detrimental effect on police efficiency”. The documents add that forces complained that “a once effective tactic now delivered outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month public review on its proposals to widen the use of biometric scanning systems. The minister for police Sarah Jones has labeled the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the independent scrutiny and oversight board for the national policing equality strategy, commented: “There was scant consideration through race action plan meetings of the facial recognition rollout even with clear relevance with the plan’s concerns.

“These revelations show yet again that the anti-racism commitments policing has undertaken through the equality initiative are not being translated into wider practice. Independent assessments have warned that innovative tools are being rolled out in a context where racial disparities, weak scrutiny and poor data collection already persist.

“Any use of facial recognition must meet strict national standards, be independently scrutinised, and demonstrate it reduces rather than compounds ethnic bias.”

Home Office Response

A government representative stated: “The Home Office treat the findings of the report with utmost gravity and we have implemented changes. A updated software has been externally evaluated and procured, which has demonstrated no measurable discrimination. It will be tested early next year and will be undergo further assessment.

“The foremost aim is ensuring public safety. This revolutionary tool will support officers to put criminals and rapists behind bars. There is officer review in each stage of the procedure and no further action would be pursued without trained officers carefully reviewing the results.”