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Police forces across the UK successfully lobbied to deploy a face scanning system known to be discriminatory against women, youths, and individuals from ethnic minority groups, following complaints that a less biased 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 person of interest against a database of over 19 million mugshots to identify potential matches.

Admitted Bias

The Home Office admitted last week that the technology was flawed. This admission followed a review by the National Physical Laboratory (NPL) determined it incorrectly matched Black and Asian people and women at much greater frequency than white men. The ministry said it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users tolerate biases in ethnicity and sex. Convenience is a poor argument for disregarding fundamental rights.”

Known Issue

Internal documents reveal that this discriminatory flaw has been known about for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was designed to mitigate the problem.

Police bosses were notified of the algorithmic discrimination in late 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 response, the National Police Chiefs’ Council (NPCC) ordered that the accuracy setting required for possible hits be raised to a point where the bias was significantly reduced.

However, this directive was reversed the next month following complaints from police that the adjusted system was generating fewer “investigative leads”. Internal records indicate the stricter setting cut the number of queries resulting in possible identifications from over half to a mere under 15%.

Severe Disparities

Although the authorities refused to say what threshold is currently used, the latest independent review discovered the system could generate false positives for Black women nearly a hundred times more often than for Caucasian women at specific configurations.

The Home Office stated on these findings: “Our evaluation found that in a specific scenarios the software is has a greater tendency to incorrectly include some population segments in its search results.”

Balancing Utility and Fairness

Outlining the impact of the brief increase to the system's accuracy setting, the NPCC documents note: “The change significantly reduces the effect of bias across protected characteristics of race, generation and gender but had a substantially detrimental effect on operational effectiveness”. The documents add that police units argued that “a previously useful tool returned results of limited benefit”.

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 described the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the advisory panel for the police race action plan, said: “We observed scant discussion in equality strategy sessions of the facial recognition rollout even with clear relevance with the plan’s concerns.

“This disclosure show once again that the anti-racism commitments policing has made through the race action plan are failing to be integrated into wider practice. Our reports have warned that new technologies are being rolled out in a context where racial disparities, weak scrutiny and poor data collection continue to exist.

“Any use of facial recognition must adhere to strict national standards, be independently scrutinised, and demonstrate it reduces rather than exacerbates racial disparity.”

Official Statement

A Home Office spokesperson stated: “We 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 trialled early next year and will be undergo further assessment.

“The foremost aim is ensuring public safety. This gamechanging technology will support officers to put criminals and rapists behind bars. There is officer review in each stage of the process and no arrest or charge would be pursued without trained officers meticulously examining the output.”