🔗 Share this article

Law enforcement agencies across the UK effectively campaigned to deploy a facial recognition 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

British police use the national police database to carry out retrospective facial recognition searches. This process entails comparing a “probe image” of a person of interest against a database of more than 19 million custody photos to find potential matches.

Admitted Bias

The UK interior ministry conceded last week that the system was biased. This admission came after a study by the government's National Physical Laboratory determined it misidentified Black and Asian people and females at significantly higher rates than white men. The Home Office stated it “had acted on the findings”.

“It prompts the question of whether this technology only becomes effective if users tolerate biases in race and sex. Convenience is a poor argument for disregarding fundamental rights.”

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.

Police bosses were informed of the system's bias in late 2024. The Home Office-commissioned NPL review found the system was had a higher probability to suggest false positives for images depicting females, individuals of Black ethnicity, 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 point where the disparity was greatly diminished.

However, this directive was reversed the next month after forces complained that the adjusted system was generating fewer “useful lines of inquiry”. NPCC documents indicate the higher threshold reduced the proportion of queries resulting in potential matches from over half to a just 14%.

Severe Disparities

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

The ministry commented on these findings: “The testing identified that in a specific scenarios the software is more likely to wrongly flag some population segments in its match reports.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents note: “This adjustment greatly lessens the effect of discrimination across protected characteristics of ethnicity, generation and sex but had a substantially detrimental effect on police efficiency”. The papers add that police units argued that “a once effective tactic returned results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a ten-week public review on its plans to widen the use of facial recognition technology. The minister for police the relevant minister has labeled the technology as the “most significant advance since genetic fingerprinting”.

Expert and Oversight Concerns

Abimbola Johnson, head of the advisory panel for the national policing equality strategy, said: “We observed scant consideration through race action plan meetings of the facial recognition rollout even with clear relevance with the strategy's goals.

“This disclosure show once again that the pledges to combat discrimination the police has made via the race action plan are not being translated into wider practice. Independent assessments have cautioned that innovative tools are being rolled out in a landscape where racial disparities, inadequate oversight and poor data collection already persist.

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

Home Office Response

A government representative said: “We takes the findings of the report 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 trialled early next year and will be subject to evaluation.

“The foremost aim is ensuring public safety. This revolutionary tool will support police to put criminals and rapists behind bars. There is officer review in every step of the process and no arrest or charge would be taken without specialist personnel carefully reviewing the output.”