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Police forces across the United Kingdom effectively campaigned to use a face scanning system acknowledged as biased against women, youths, and members of minority ethnic backgrounds, after complaining that a less biased version generated a reduced number of investigative leads.

The Technology in Practice

UK forces utilize the police national database (PND) to carry out searches using historical face recognition. This process entails comparing a “probe image” of a suspect against a repository of over 19 million custody photos to identify potential matches.

Admitted Bias

The UK interior ministry conceded last week that the system was biased. This acknowledgment came after a review by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and females at much greater frequency than Caucasian males. The ministry said it “had acted on the findings”.

“This raises the issue of whether this technology only becomes useful if users tolerate biases in ethnicity and gender. Convenience is a weak argument for overriding basic freedoms.”

Known Issue

Official papers reveal that this discriminatory flaw has been known about for over twelve months. Furthermore, police forces lobbied to reverse an initial decision that was intended to mitigate the problem.

Senior officers were notified of the algorithmic discrimination in September 2024. The government-ordered laboratory study found the system was had a higher probability to produce false positives for photos of women, Black people, and those aged 40 and under.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for possible hits be increased to a level where the bias was significantly reduced.

However, this decision was reversed the next month after forces complained that the adjusted system was generating a lower number of “investigative leads”. NPCC documents show the stricter setting reduced the number of searches resulting in possible identifications from 56% to a mere 14%.

Profound Inequalities

Although the authorities declined to specify what threshold is now in operation, the latest NPL study found the system could produce incorrect matches for Black women nearly a hundred times more often than for Caucasian women at certain settings.

The Home Office stated on these findings: “The testing found that in a limited set of circumstances the software is has a greater tendency to incorrectly include some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Describing the impact of the temporary raise to the system's confidence threshold, the police records state: “The change greatly lessens the impact of bias across legally safeguarded attributes of race, generation and sex but had a substantially detrimental effect on operational effectiveness”. The papers further note that police units complained that “a once effective tactic now delivered outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a two-and-a-half-month consultation on its plans to expand the use of biometric scanning systems. Policing minister the relevant minister has labeled the technology 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, commented: “There was very little consideration through equality strategy sessions of the technology deployment even with clear relevance with the plan’s concerns.

“This disclosure demonstrate once again that the anti-racism commitments policing has made via the equality initiative are not being translated into broader operations. Independent assessments have warned that new technologies are being rolled out in a landscape where ethnic inequalities, weak scrutiny and poor data collection continue to exist.

“Any use of this technology must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it reduces rather than compounds racial disparity.”

Official Statement

A government representative stated: “The Home Office treat the conclusions of the report with utmost gravity and we have already taken action. 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 apprehend and prosecute offenders. There is human involvement in each stage of the process and no arrest or charge would be pursued without specialist personnel carefully reviewing the output.”