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Law enforcement agencies across the UK effectively campaigned to deploy a face scanning system acknowledged as biased against females, young people, and members of minority ethnic backgrounds, after complaining that a less biased version produced fewer potential suspects.

The Technology in Practice

British police utilize the national police database to carry out searches using historical face recognition. This procedure involves matching a “probe image” of a person of interest against a database of more than 19 million custody photos to find possible hits.

Admitted Bias

The UK interior ministry admitted last week that the system was biased. This acknowledgment came after a study by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and women at much greater frequency than white men. The ministry said it “took steps on the findings”.

“It prompts the issue of whether facial recognition only becomes useful if users tolerate discrimination in ethnicity and gender. Operational ease is a weak argument for overriding fundamental rights.”

Known Issue

Official papers reveal that this bias has been known about for more than a year. Furthermore, police forces lobbied to reverse an earlier ruling that was intended to address the problem.

Police bosses were informed of the system's bias in September 2024. The government-ordered NPL review found the system was more likely to suggest false positives for photos of women, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

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

However, this decision was reversed the next month after forces complained that the modified technology was producing a lower number of “useful lines of inquiry”. NPCC documents indicate the higher threshold reduced the number of searches that yielded potential matches from 56% to a just 14%.

Profound Inequalities

Although the Home Office and NPCC declined to specify what setting is currently used, the latest NPL study discovered the system could produce false positives for Black women almost 100 times more frequently than for white women at certain settings.

The ministry commented on these findings: “The testing identified that in a limited set of circumstances the software is more likely to wrongly flag some population segments in its match reports.”

Operational Effectiveness vs. Bias

Describing the impact of the brief increase to the system's confidence threshold, the police records note: “This adjustment 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 documents further note that forces argued that “a previously useful tool now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month public review on its plans to widen the use of biometric scanning systems. The minister for police Sarah Jones has described the tool as the “most significant advance since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the national policing equality strategy, said: “We observed scant consideration through race action plan meetings of the technology deployment despite obvious cross-over with the plan’s concerns.

“These revelations demonstrate once again that the pledges to combat discrimination policing has made via the race action plan are not being translated into wider practice. Independent assessments have cautioned that new technologies are being implemented in a context where racial disparities, weak scrutiny and poor data collection already persist.

“All deployment of facial recognition must meet rigorous official guidelines, be subject to external review, and prove it diminishes rather than exacerbates racial disparity.”

Official Statement

A Home Office spokesperson stated: “We treat the findings of the study with utmost gravity and we have implemented changes. A updated software has been independently tested and procured, which has demonstrated no measurable discrimination. It will be tested early next year and will be subject to further assessment.

“The foremost aim is protecting the public. This gamechanging technology will support officers to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no further action would be taken without specialist personnel carefully reviewing the output.”