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Police forces across the UK effectively campaigned to use a face scanning system known to be biased against women, young people, and members of ethnic minority groups, following complaints that a more accurate version generated a reduced number of investigative leads.

The Technology in Practice

British police use the national police database to conduct retrospective facial recognition searches. This process involves matching a reference photograph of a suspect against a database of over 19 million custody photos to identify possible hits.

Acknowledged Discrimination

The UK interior ministry conceded last week that the system was biased. This admission followed a study by the National Physical Laboratory (NPL) determined it incorrectly matched people of Black and Asian heritage and women at much greater frequency than white men. The ministry stated it “took steps on the findings”.

“It prompts the question of whether this technology only becomes useful if users tolerate biases in ethnicity and sex. Operational ease is a weak argument for overriding basic freedoms.”

Known Issue

Official papers show that this discriminatory flaw has been recognized for over twelve months. Furthermore, police forces lobbied to reverse an earlier ruling that was designed to address the problem.

Senior officers were notified of the system's bias in late 2024. The Home Office-commissioned NPL review concluded the system was more likely to suggest false positives for photos of females, Black people, and those aged 40 and under.

A Policy U-Turn

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

However, this directive was overturned the next month following complaints from police that the modified technology was producing a lower number of “useful lines of inquiry”. Internal records show the higher threshold cut the number of searches resulting in potential matches from over half to a just under 15%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold is currently used, the latest NPL study discovered the system could produce false positives for women of Black heritage almost 100 times more often than for Caucasian women at specific configurations.

The ministry commented on these results: “Our evaluation found that in a limited set of circumstances the software is more likely to incorrectly include some demographic groups in its match reports.”

Balancing Utility and Fairness

Describing the effect of the brief increase to the system's accuracy setting, the NPCC documents note: “The change greatly lessens the effect of bias across protected characteristics of race, age and gender but had a substantially detrimental effect on operational effectiveness”. The documents add that police units complained that “a once effective tactic now delivered results of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a two-and-a-half-month consultation on its plans to expand the use of facial recognition technology. Policing minister Sarah Jones has labeled the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, head of the independent scrutiny and oversight board for the police race action plan, said: “We observed scant consideration through race action plan meetings of the technology deployment even with obvious cross-over with the strategy's goals.

“These revelations demonstrate once again that the pledges to combat discrimination policing has undertaken through the equality initiative are not being translated into wider practice. Independent assessments have warned that new technologies are being rolled out in a context where racial disparities, weak scrutiny and poor data collection already persist.

“All deployment of this technology must adhere to strict national standards, be subject to external review, and demonstrate it diminishes rather than compounds racial disparity.”

Home Office Response

A Home Office spokesperson said: “The Home Office takes the conclusions of the study seriously and we have implemented changes. A new algorithm has been independently tested and acquired, which has no statistically significant bias. It will be tested in the coming months and will be subject to evaluation.

“Our priority is ensuring public safety. This gamechanging technology will support officers to put criminals and rapists behind bars. There is officer review in every step of the procedure and no arrest or charge would be taken without trained officers meticulously examining the output.”