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Law enforcement agencies across the UK successfully lobbied to deploy a face scanning system acknowledged as biased against women, young people, and members of minority ethnic backgrounds, after complaining that a less biased version generated fewer potential suspects.

The Technology in Practice

UK forces utilize the police national database (PND) to conduct retrospective facial recognition searches. This procedure entails comparing a reference photograph of a suspect against a database of more than 19 million mugshots to find possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the system was flawed. This acknowledgment came after a review by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and females at significantly higher rates than Caucasian males. The Home Office said it “had acted on the findings”.

“This raises the question of whether facial recognition only becomes effective if users tolerate biases in race and gender. Convenience is a poor argument for disregarding fundamental rights.”

Known Issue

Official papers show that this bias has been recognized for over twelve months. Furthermore, police forces lobbied to reverse an initial decision that was intended to mitigate the problem.

Police bosses were informed of the system's bias in September 2024. The Home Office-commissioned laboratory study found the system was had a higher probability to produce false positives for photos of 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 accuracy setting required for potential matches be raised to a level where the bias was significantly reduced.

However, this decision was reversed the next month after forces complained that the modified technology was generating a lower number of “investigative leads”. NPCC documents indicate the higher threshold cut the number of searches that yielded potential matches from over half to a mere 14%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is currently used, the recent NPL study discovered the system could generate incorrect matches for women of Black heritage nearly a hundred times more often than for white women at specific configurations.

The Home Office stated on these findings: “Our evaluation identified that in a limited set of circumstances the algorithm is more likely to incorrectly include some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Outlining the effect of the brief increase to the system's accuracy setting, the police records state: “The change greatly lessens the effect of discrimination across protected characteristics of ethnicity, age and sex but had a substantially detrimental effect on police efficiency”. The documents add that police units argued that “a previously useful tool now delivered outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a two-and-a-half-month consultation on its plans to expand the use of biometric scanning systems. Policing minister the relevant minister has described the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, head of the independent scrutiny and oversight board for the police race action plan, said: “We observed very little consideration through equality strategy sessions of the facial recognition rollout even with 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 not being translated into broader operations. Our reports have warned that innovative tools are being implemented in a context where ethnic inequalities, weak scrutiny and faulty information gathering already persist.

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

Home Office Response

A Home Office spokesperson stated: “We takes the findings of the study seriously and we have already taken action. A new algorithm has been independently tested and acquired, which has no statistically significant bias. It will be tested early next year and will be undergo further assessment.

“The foremost aim is ensuring public safety. This revolutionary tool will assist police to apprehend and prosecute offenders. There is officer review in every step of the procedure and no arrest or charge would be pursued without specialist personnel carefully reviewing the output.”