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Police forces across the UK effectively campaigned to deploy a face scanning system acknowledged as discriminatory against females, youths, and members of minority ethnic backgrounds, following complaints that a more accurate version produced fewer potential suspects.

The Technology in Practice

British police use the police national database (PND) to carry out retrospective facial recognition searches. This process entails matching a “probe image” of a person of interest against a repository of more than 19 million custody photos to identify possible hits.

Admitted Bias

The Home Office admitted last week that the technology was biased. This admission followed a review by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and females at much greater frequency than white men. The ministry stated it “took steps on the findings”.

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

Long-Standing Problem

Official papers reveal that this discriminatory flaw has been known about for more than a year. Furthermore, law enforcement lobbied to reverse an initial decision that was intended to address the problem.

Senior officers were informed of the system's bias in late 2024. The government-ordered laboratory study found the system was more likely to produce incorrect matches for images depicting females, Black people, and those aged 40 and under.

A Policy U-Turn

In response, the national police leadership body mandated that the confidence threshold required for potential matches be increased to a level where the disparity was greatly diminished.

However, this decision was overturned the next month after forces complained that the modified technology was generating a lower number of “investigative leads”. NPCC documents show the stricter setting reduced the proportion 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 currently used, the recent NPL study found the system could produce false positives for Black women almost 100 times more often than for white women at specific configurations.

The Home Office commented on these results: “Our evaluation identified that in a specific scenarios the algorithm is more likely to wrongly flag some demographic groups in its match reports.”

Balancing Utility and Fairness

Describing the impact of the temporary raise to the system's accuracy setting, the police records note: “This adjustment significantly reduces the effect of bias across legally safeguarded attributes of race, generation and sex but had a substantially detrimental effect on operational effectiveness”. The papers further note that police units argued that “a once effective tactic now delivered results of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a two-and-a-half-month public review on its plans to widen the use of biometric scanning systems. The minister for police the relevant minister has described the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “We observed very little consideration through race action plan meetings of the technology deployment despite clear relevance with the strategy's goals.

“These revelations demonstrate once again that the pledges to combat discrimination the police has undertaken via the equality initiative are not being translated into broader operations. Independent assessments have warned that innovative tools are being rolled out in a landscape where racial disparities, inadequate oversight and poor data collection continue to exist.

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

Home Office Response

A Home Office spokesperson stated: “The Home Office treat the conclusions 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 undergo evaluation.

“The foremost aim is protecting the public. This gamechanging technology will support police to put criminals and rapists behind bars. There is officer review in every step of the procedure and no further action would be taken without trained officers meticulously examining the results.”