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Police forces across the United Kingdom effectively campaigned to use a face scanning system acknowledged as biased against females, youths, and members of ethnic minority groups, after complaining that a more accurate version produced fewer investigative leads.

How the System Works

UK forces use the national police database to conduct retrospective facial recognition searches. This process entails matching a “probe image” of a person of interest against a repository of more than 19 million mugshots to find potential matches.

Admitted Bias

The Home Office conceded last week that the system was biased. This admission came after a review by the government's National Physical Laboratory determined it misidentified Black and Asian people and females at much greater frequency than white men. The Home Office stated it “took steps on the findings”.

“It prompts the issue of whether facial recognition only becomes useful if users tolerate biases in race and gender. Operational ease is a weak argument for disregarding basic freedoms.”

Known Issue

Official papers show that this bias has been known about for more than a year. Furthermore, police forces lobbied to reverse an earlier ruling that was designed to address the problem.

Senior officers were informed of the algorithmic discrimination in late 2024. The Home Office-commissioned NPL review found the system was had a higher probability to suggest incorrect matches for photos of women, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

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

However, this decision was reversed the following month following complaints from police that the adjusted system was producing a lower number of “useful lines of inquiry”. Internal records show the higher threshold cut the number of queries that yielded potential matches from over half to a mere 14%.

Severe Disparities

Although the authorities declined to specify what threshold is currently used, the latest independent review found the system could produce false positives for Black women almost 100 times more often than for white 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.”

Balancing Utility and Fairness

Outlining the impact of the temporary raise to the system's confidence threshold, the NPCC documents state: “This adjustment greatly lessens the impact of bias across legally safeguarded attributes of race, age and sex but had a substantially detrimental effect on operational effectiveness”. The papers add that police units argued that “a previously useful tool returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a two-and-a-half-month consultation on its proposals to widen the use of biometric scanning systems. Policing minister Sarah Jones has described the tool 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: “There was scant consideration through race action plan meetings of the facial recognition rollout despite clear relevance with the strategy's goals.

“These revelations demonstrate once again that the anti-racism commitments policing has made via the race action plan are failing to be integrated into wider practice. Independent assessments have cautioned that new technologies are being implemented in a landscape where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

“Any use of this technology must adhere to rigorous official guidelines, be subject to external review, and demonstrate it diminishes rather than compounds ethnic bias.”

Home Office Response

A Home Office spokesperson said: “The Home Office treat the findings of the study with utmost gravity and we have already taken action. A new algorithm has been independently tested and acquired, which has no statistically significant bias. It will be trialled in the coming months and will be subject to further assessment.

“The foremost aim is protecting the public. This revolutionary tool 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 meticulously examining the results.”