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Police forces across the UK effectively campaigned to use a face scanning system known to be discriminatory against women, youths, and individuals from minority ethnic backgrounds, after complaining that a more accurate version generated fewer potential suspects.

How the System Works

UK forces utilize the police national database (PND) to carry out retrospective facial recognition searches. This procedure entails matching a reference photograph of a person of interest against a database of over 19 million mugshots to find possible hits.

Admitted Bias

The UK interior ministry admitted last week that the technology was biased. This admission came after a study by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and women at significantly higher rates than Caucasian males. The Home Office stated it “had acted on the findings”.

“This raises the question of whether this technology only becomes effective if users accept biases in race and gender. Convenience is a poor argument for disregarding basic freedoms.”

Known Issue

Official papers show that this discriminatory flaw has been recognized for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was intended to mitigate the problem.

Senior officers were notified of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study found the system was had a higher probability to suggest false positives for images depicting women, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches be raised to a level where the bias was significantly reduced.

However, this decision was reversed the following month after forces complained that the adjusted system was producing a lower number of “useful lines of inquiry”. NPCC documents show the stricter setting cut the number of searches resulting in potential matches from 56% to a mere under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is now in operation, the latest independent review discovered the system could produce false positives for Black women almost 100 times more frequently than for Caucasian women at certain settings.

The ministry commented on these results: “The testing identified that in a specific scenarios the algorithm is more likely to incorrectly include some population segments in its search results.”

Operational Effectiveness vs. Bias

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents note: “The change greatly lessens the effect of bias across protected characteristics of ethnicity, generation and gender but had a substantially detrimental effect on operational effectiveness”. The papers add that police units complained 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 consultation on its proposals to expand the use of biometric scanning systems. The minister for police the relevant minister has described the tool as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the national policing equality strategy, said: “There was scant discussion in race action plan meetings of the facial recognition rollout despite obvious cross-over with the plan’s concerns.

“These revelations show yet again that the anti-racism commitments policing has made via the equality initiative are not being translated into wider practice. Our reports have warned that innovative tools are being implemented in a context where racial disparities, inadequate oversight and poor data collection already persist.

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

Home Office Response

A government representative stated: “We treat the conclusions of the study seriously and we have already taken action. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be tested early next year and will be subject to evaluation.

“Our priority is ensuring public safety. This gamechanging technology will support officers to apprehend and prosecute offenders. There is human involvement in every step of the process and no further action would be taken without trained officers meticulously examining the results.”