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Police forces across the United Kingdom effectively campaigned to use a face scanning system known to be biased against females, youths, and individuals from ethnic minority groups, after complaining that a more accurate version produced a reduced number of investigative leads.

How the System Works

British police utilize the police national database (PND) to conduct searches using historical face recognition. This process entails matching a reference photograph of a person of interest against a database of more than 19 million mugshots to identify potential matches.

Admitted Bias

The UK interior ministry admitted last week that the system was flawed. This acknowledgment followed a review by the government's National Physical Laboratory determined it incorrectly matched Black and Asian people and females at much greater frequency than white men. The ministry said it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users tolerate biases in race and gender. Operational ease is a poor argument for overriding basic freedoms.”

Long-Standing Problem

Official papers reveal that this bias 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 informed of the algorithmic discrimination in September 2024. The Home Office-commissioned NPL review concluded the system was more likely to produce false positives for images depicting females, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches be raised to a point where the disparity was significantly reduced.

However, this directive was reversed 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 proportion of searches that yielded possible identifications from 56% to a just under 15%.

Profound Inequalities

Although the authorities declined to specify what setting is now in operation, the recent NPL study found the system could produce false positives for Black women nearly a hundred times more frequently than for white women at specific configurations.

The Home Office commented on these results: “Our evaluation found that in a specific scenarios the algorithm is has a greater tendency to incorrectly include some population segments in its search results.”

Operational Effectiveness vs. Bias

Outlining the effect of the temporary raise to the system's confidence threshold, the NPCC documents state: “This adjustment significantly reduces the effect of bias across legally safeguarded attributes of ethnicity, generation and sex but had a substantially detrimental effect on police efficiency”. The papers add that police units complained that “a once effective tactic now delivered outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a two-and-a-half-month public review on its proposals to expand the use of facial recognition technology. Policing minister Sarah Jones has described 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 race action plan meetings of the facial recognition rollout despite obvious cross-over with the plan’s concerns.

“These revelations show 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 innovative tools are being rolled out in a landscape where ethnic inequalities, weak scrutiny and faulty information gathering already persist.

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

Home Office Response

A Home Office spokesperson said: “We takes the conclusions of the report seriously and we have already taken action. A updated software has been externally evaluated and acquired, which has no statistically significant bias. It will be trialled early next year and will be undergo evaluation.

“The foremost aim is protecting the public. This revolutionary tool will assist police to put criminals and rapists behind bars. There is human involvement in each stage of the process and no arrest or charge would be pursued without specialist personnel carefully reviewing the results.”