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Police forces across the United Kingdom successfully lobbied to use a facial recognition system acknowledged as discriminatory against women, youths, and individuals from ethnic minority groups, after complaining that a more accurate version produced fewer investigative leads.

The Technology in Practice

UK forces use the police national database (PND) to carry out retrospective facial recognition searches. This process involves matching a reference photograph 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 technology was biased. This admission came after a review by the National Physical Laboratory (NPL) determined it incorrectly matched people of Black and Asian heritage and females at much greater frequency than Caucasian males. The Home Office stated it “took steps on the findings”.

“This raises the issue of whether facial recognition only becomes effective if users accept biases in race and sex. Operational ease is a weak argument for overriding fundamental rights.”

Known Issue

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

Senior officers were notified of the system's bias in September 2024. The government-ordered NPL review concluded the system was more likely to produce incorrect matches for photos of women, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In response, the National Police Chiefs’ Council (NPCC) mandated that the accuracy setting required for potential matches be increased to a point where the bias was significantly reduced.

However, this decision was overturned the following month following complaints from police that the adjusted system was producing fewer “investigative leads”. Internal records show the higher threshold reduced the number of searches resulting in possible identifications from over half to a just 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what setting is currently used, the recent NPL study discovered the system could generate false positives for Black women nearly a hundred times more frequently than for Caucasian women at specific configurations.

The ministry commented on these findings: “Our evaluation identified that in a specific scenarios the software is more likely to wrongly flag some population segments in its search results.”

Operational Effectiveness vs. Bias

Outlining the impact of the temporary raise to the system's confidence threshold, the NPCC documents state: “The change significantly reduces the impact of bias across protected characteristics of race, generation and gender but had a significant negative impact on operational effectiveness”. The documents add that police units argued that “a once effective tactic now delivered outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a two-and-a-half-month public review on its proposals to expand the use of facial recognition technology. 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 independent scrutiny and oversight board for the national policing equality strategy, said: “We observed very little consideration through equality strategy sessions of the facial recognition rollout despite clear relevance with the plan’s concerns.

“These revelations show yet again that the anti-racism commitments the police has made through the equality initiative are not being translated into wider practice. Independent assessments have cautioned that new technologies are being rolled out in a landscape where racial disparities, weak scrutiny and poor data collection already persist.

“All deployment of facial recognition must meet strict national standards, be independently scrutinised, and prove it diminishes rather than exacerbates ethnic bias.”

Home Office Response

A government representative stated: “The Home Office treat the conclusions of the study with utmost gravity and we have implemented changes. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be trialled early next year and will be undergo further assessment.

“The foremost aim is ensuring public safety. This gamechanging technology will support officers to put criminals and rapists behind bars. There is human involvement in every step of the process and no arrest or charge would be pursued without trained officers carefully reviewing the results.”