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Police forces across the UK successfully lobbied to use a facial recognition system acknowledged as discriminatory against females, young people, and members of minority ethnic backgrounds, after complaining that a less biased version produced fewer investigative leads.

How the System Works

British police use the national police database to carry out retrospective facial recognition searches. This procedure entails comparing a “probe image” of a suspect against a repository of over 19 million mugshots to identify possible hits.

Admitted Bias

The UK interior ministry conceded last week that the system was flawed. This admission came after a review by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and females at significantly higher rates than Caucasian males. The ministry said it “took steps on the findings”.

“It prompts the question of whether this technology only becomes effective if users tolerate discrimination in race and sex. Operational ease is a poor argument for overriding fundamental rights.”

Known Issue

Internal documents reveal that this bias has been recognized for more than a year. Furthermore, law enforcement argued to overturn an earlier ruling that was designed to mitigate the problem.

Senior officers were notified of the system's bias in late 2024. The government-ordered laboratory study found the system was more likely to suggest false positives for images depicting women, Black people, and those aged 40 and under.

A Policy U-Turn

In reaction, the national police leadership body mandated that the accuracy setting required for possible hits be raised to a point where the bias was greatly diminished.

However, this directive was overturned the following month after forces complained that the modified technology was producing fewer “investigative leads”. Internal records show the higher threshold reduced the proportion of searches that yielded potential matches from 56% to a just 14%.

Profound Inequalities

Although the authorities declined to specify what threshold is currently used, the recent independent review discovered the system could generate false positives for Black women almost 100 times more frequently than for Caucasian women at specific configurations.

The Home Office commented on these findings: “The testing identified that in a limited set of circumstances the algorithm is more likely to wrongly flag some population segments in its match reports.”

Operational Effectiveness vs. Bias

Describing the impact of the temporary raise to the system's accuracy setting, the NPCC documents note: “This adjustment significantly reduces the effect of discrimination across legally safeguarded attributes of race, age and sex but had a substantially detrimental effect on operational effectiveness”. The papers further note 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 widen the use of biometric scanning systems. Policing minister Sarah Jones 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 scant consideration in race action plan meetings of the technology deployment even with obvious cross-over with the plan’s concerns.

“These revelations show yet again that the anti-racism commitments the police has made via the equality initiative are failing to be integrated into broader operations. Our reports have warned that innovative tools are being rolled out in a landscape where ethnic inequalities, weak scrutiny and faulty information gathering continue to exist.

“All deployment of facial recognition must meet strict national standards, be independently scrutinised, and demonstrate it diminishes rather than exacerbates racial disparity.”

Home Office Response

A Home Office spokesperson stated: “We takes the findings of the report with utmost gravity and we have implemented changes. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be trialled early next year and will be undergo evaluation.

“Our priority is protecting the public. This revolutionary tool will assist officers to put criminals and rapists behind bars. There is human involvement in each stage of the process and no arrest or charge would be taken without trained officers meticulously examining the output.”