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Police forces across the UK successfully lobbied to use a face scanning system acknowledged as biased against females, young people, and individuals from ethnic minority groups, after complaining that a more accurate version generated a reduced number of potential suspects.

The Technology in Practice

UK forces use the national police database to carry out retrospective facial recognition searches. This procedure entails matching a “probe image” of a suspect against a repository of over 19 million custody photos to find potential matches.

Acknowledged Discrimination

The UK interior ministry conceded last week that the technology was biased. This admission came after a study by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and females at significantly higher rates than white men. The Home Office stated it “took steps on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users accept biases in ethnicity and sex. Operational ease is a poor argument for overriding fundamental rights.”

Known Issue

Internal documents show that this discriminatory flaw has been known about for more than a year. Furthermore, police forces lobbied to reverse an initial decision that was intended to address the problem.

Senior officers were notified of the system's bias in late 2024. The Home Office-commissioned NPL review found the system was more likely to produce incorrect matches for images depicting females, Black people, and those under 40 years old.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) mandated that the accuracy setting required for potential matches be increased to a point where the disparity was greatly diminished.

However, this directive was overturned the next month after forces complained that the adjusted system was producing a lower number of “useful lines of inquiry”. Internal records indicate the higher threshold cut the proportion of searches that yielded possible identifications from over half to a mere under 15%.

Severe Disparities

Although the Home Office and NPCC declined to specify what setting is now in operation, the latest NPL study discovered the system could produce incorrect matches for Black women almost 100 times more often than for Caucasian women at specific configurations.

The ministry stated on these findings: “Our evaluation found 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 effect of the brief increase to the system's accuracy setting, the police records note: “This adjustment significantly reduces the effect of discrimination across legally safeguarded attributes of race, age and gender but had a substantially detrimental effect on police efficiency”. The papers add that police units argued that “a previously useful tool returned results of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has opened a ten-week public review on its proposals to widen the use of biometric scanning systems. The minister for police the relevant minister has described the technology as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, head of the independent scrutiny and oversight board for the national policing equality strategy, said: “There was very little discussion in race action plan meetings of the technology deployment even with obvious cross-over with the strategy's goals.

“These revelations demonstrate once again that the anti-racism commitments policing has made through the race action plan are failing to be integrated into wider practice. Our reports have cautioned that innovative tools are being rolled out in a landscape where ethnic inequalities, inadequate oversight and faulty information gathering already persist.

“Any use of facial recognition must meet rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than compounds racial disparity.”

Home Office Response

A Home Office spokesperson said: “We treat the conclusions of the study with utmost gravity and we have implemented changes. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be tested early next year and will be subject to evaluation.

“Our priority is protecting the public. This revolutionary tool will support police to put criminals and rapists behind bars. There is officer review in every step of the procedure and no arrest or charge would be taken without specialist personnel meticulously examining the output.”