🔗 Share this article

Police forces across the UK effectively campaigned to deploy a facial recognition system known to be discriminatory against women, young people, and individuals from minority ethnic backgrounds, after complaining that a more accurate version produced fewer potential suspects.

How the System Works

British police utilize the national police database to carry out searches using historical face recognition. This procedure involves comparing a “probe image” of a person of interest against a repository of over 19 million custody photos to find potential matches.

Admitted Bias

The Home Office conceded last week that the technology was flawed. This acknowledgment followed a study by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and females at much greater frequency than white men. The Home Office said it “had acted on the findings”.

“It prompts the question of whether facial recognition only becomes useful if users tolerate biases in ethnicity and sex. Convenience is a poor argument for disregarding basic freedoms.”

Known Issue

Internal documents show that this bias has been known about for over twelve months. Furthermore, police forces lobbied to reverse an initial decision that was designed to mitigate the problem.

Senior officers were informed of the system's bias in late 2024. The government-ordered laboratory study found the system was had a higher probability to produce incorrect matches for images depicting females, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

In reaction, the national police leadership body mandated that the confidence threshold required for possible hits be raised to a level where the disparity was greatly diminished.

However, this decision was reversed the next month following complaints from police that the adjusted system was producing a lower number of “investigative leads”. Internal records indicate the higher threshold cut the number of searches that yielded possible identifications from 56% to a just 14%.

Profound Inequalities

Although the Home Office and NPCC refused to say what setting is now in operation, the recent NPL study discovered the system could produce incorrect matches for Black women nearly a hundred times more frequently than for white women at specific configurations.

The Home Office stated on these findings: “The testing found that in a specific scenarios the software is has a greater tendency to incorrectly include some population segments in its search results.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents note: “The change significantly reduces the impact of bias across legally safeguarded attributes of ethnicity, age and sex but had a significant negative impact on police efficiency”. The papers further note that police units complained that “a previously useful tool now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has opened a ten-week public review on its proposals to expand the use of facial recognition technology. The minister for police Sarah Jones has labeled the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the national policing equality strategy, commented: “There was scant consideration in equality strategy sessions of the facial recognition rollout despite obvious cross-over with the strategy's goals.

“This disclosure show yet again that the anti-racism commitments policing has undertaken via the equality initiative are failing to be integrated into broader operations. Our reports have warned that innovative tools are being implemented in a landscape where racial disparities, inadequate oversight and faulty information gathering already persist.

“Any use of this technology must meet rigorous official guidelines, be independently scrutinised, and prove it reduces rather than exacerbates racial disparity.”

Official Statement

A government representative stated: “We treat the conclusions of the study seriously and we have already taken action. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be trialled early next year and will be undergo evaluation.

“Our priority is protecting the public. This gamechanging technology will support officers to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no further action would be taken without specialist personnel carefully reviewing the output.”