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Law enforcement agencies across the UK successfully lobbied to use a facial recognition system known to be biased against females, youths, and members of minority ethnic backgrounds, following complaints that a more accurate version produced a reduced number of potential suspects.

How the System Works

UK forces utilize the police national database (PND) to conduct retrospective facial recognition searches. This process involves comparing a “probe image” of a person of interest against a repository of over 19 million custody photos to find possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the system was biased. This admission came after a study by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and women at significantly higher rates than Caucasian males. The Home Office said it “took steps on the findings”.

“This raises the question of whether this technology only becomes useful if users tolerate biases in race and sex. Convenience is a weak argument for disregarding basic freedoms.”

Long-Standing Problem

Internal documents reveal that this bias has been recognized for over twelve months. Furthermore, police forces argued to overturn an initial decision that was intended to mitigate the problem.

Police bosses were notified of the system's bias in late 2024. The Home Office-commissioned laboratory study concluded the system was more likely to produce incorrect matches for photos of women, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the accuracy setting required for potential matches be increased to a point where the disparity was greatly diminished.

However, this decision was overturned the next month after forces complained that the modified technology was generating fewer “investigative leads”. NPCC documents show the higher threshold reduced the number of searches resulting in potential matches from over half to a just 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is now in operation, the latest NPL study found the system could produce incorrect matches for Black women almost 100 times more often 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 algorithm is has a greater tendency to incorrectly include some population segments in its match reports.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the police records note: “The change greatly lessens the effect of discrimination across protected characteristics of race, age and gender but had a significant negative impact on operational effectiveness”. The papers add that police units argued that “a once effective tactic returned outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week public review on its plans to expand the use of biometric scanning systems. Policing minister Sarah Jones has described the tool as the “biggest breakthrough since genetic fingerprinting”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the advisory panel for the police race action plan, commented: “There was very little discussion in race action plan meetings of the facial recognition rollout despite obvious cross-over with the strategy's goals.

“This disclosure demonstrate yet 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 cautioned that innovative tools are being rolled out in a landscape where ethnic inequalities, inadequate oversight and faulty information gathering already persist.

“Any use of facial recognition must meet rigorous official guidelines, be independently scrutinised, and demonstrate it reduces rather than exacerbates racial disparity.”

Home Office Response

A government representative stated: “We 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 trialled early next year and will be subject to further assessment.

“Our priority is ensuring public safety. This gamechanging technology will support police to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no further action would be pursued without trained officers meticulously examining the results.”