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Police forces across the UK successfully lobbied to deploy a face scanning system known to be biased against females, young people, and members of minority ethnic backgrounds, after complaining that a less biased version produced fewer potential suspects.

How the System Works

UK forces utilize the police national database (PND) to conduct retrospective facial recognition searches. This procedure involves matching a reference photograph of a person of interest against a repository of more than 19 million custody photos to find possible hits.

Acknowledged Discrimination

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 incorrectly matched Black and Asian people and women at much greater frequency than white men. The Home Office said it “took steps on the findings”.

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

Known Issue

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 designed to mitigate the problem.

Police bosses were informed of the system's bias in late 2024. The government-ordered NPL review concluded the system was had a higher probability to suggest incorrect matches for images depicting females, Black people, and those under 40 years old.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) mandated that the accuracy setting required for possible hits be raised to a level where the disparity was significantly reduced.

However, this directive was overturned the following month following complaints from police that the modified technology was generating fewer “investigative leads”. NPCC documents show the higher threshold reduced the number of queries resulting in possible identifications from over half to a just under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what setting is now in operation, the recent NPL study found the system could generate false positives for women of Black heritage almost 100 times more frequently than for Caucasian women at certain settings.

The ministry commented on these findings: “The testing found that in a limited set of circumstances the software is more likely to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the impact of the brief increase to the system's confidence threshold, the NPCC documents note: “The change greatly lessens the impact of bias across protected characteristics of race, generation and sex but had a significant negative impact on police efficiency”. The documents further note that police units complained that “a once effective tactic returned outcomes 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 facial recognition technology. The minister for police the relevant minister has described the tool 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 police race action plan, said: “We observed very little consideration in race action plan meetings of the technology deployment despite clear relevance with the strategy's goals.

“This disclosure show once again that the anti-racism commitments the police has made via the equality initiative are failing to be integrated into wider practice. Our reports have cautioned that innovative tools are being rolled out in a context where ethnic inequalities, weak scrutiny and faulty information gathering already persist.

“All deployment 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 government representative said: “We treat the conclusions of the report seriously and we have implemented changes. A new algorithm has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be tested early next year and will be undergo further assessment.

“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 arrest or charge would be pursued without specialist personnel carefully reviewing the results.”