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Police forces across the UK effectively campaigned to deploy a face scanning system known to be discriminatory against women, youths, and members of minority ethnic backgrounds, after complaining that a more accurate version generated a reduced number of potential suspects.

How the System Works

UK forces use the national police database to conduct retrospective facial recognition searches. This procedure entails matching a “probe image” of a person of interest against a repository of more than 19 million custody photos to find potential matches.

Admitted Bias

The UK interior ministry conceded last week that the system was flawed. 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 issue of whether this technology only becomes effective if users tolerate biases in race and gender. Convenience is a poor argument for overriding fundamental rights.”

Long-Standing Problem

Internal documents reveal that this discriminatory flaw has been known about for over twelve months. Furthermore, law enforcement lobbied to reverse an earlier ruling that was intended to address the problem.

Senior officers were notified of the algorithmic discrimination in late 2024. The Home Office-commissioned NPL review concluded the system was more likely to suggest false positives for photos of women, Black people, and those under 40 years old.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for potential matches be raised to a point where the bias was greatly diminished.

However, this directive was reversed the next month following complaints from police that the modified technology was producing fewer “useful lines of inquiry”. NPCC documents show the higher threshold cut the proportion of queries resulting in possible identifications from 56% to a just under 15%.

Severe Disparities

Although the authorities declined to specify what threshold is currently used, the latest NPL study found the system could generate false positives for Black women nearly a hundred times more frequently than for white women at certain settings.

The ministry stated on these findings: “The testing found that in a limited set of circumstances the software is more likely to wrongly flag 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 state: “The change greatly lessens the impact of discrimination across legally safeguarded attributes of race, generation and sex but had a substantially detrimental effect on police efficiency”. The documents further note that police units argued that “a previously useful tool returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration 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 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 scant consideration through equality strategy sessions of the facial recognition rollout even with clear relevance with the plan’s concerns.

“This disclosure demonstrate once again that the anti-racism commitments the police has undertaken through the race action plan are not being translated into wider practice. Our reports have warned that innovative tools are being implemented in a context where ethnic inequalities, inadequate oversight and poor data collection already persist.

“All deployment of facial recognition must adhere to rigorous official guidelines, be subject to external review, and demonstrate it reduces rather than compounds ethnic bias.”

Home Office Response

A government representative said: “We takes the conclusions of the study with utmost gravity and we have already taken action. A new algorithm has been independently tested and acquired, which has demonstrated no measurable discrimination. It will be tested early next year and will be subject to evaluation.

“The foremost aim is ensuring public safety. This gamechanging technology will assist police 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 specialist personnel carefully reviewing the results.”