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Law enforcement agencies across the UK successfully lobbied to deploy a face scanning system acknowledged as biased against females, young people, and members of ethnic minority groups, after complaining that a more accurate version generated a reduced number of potential suspects.

How the System Works

British police utilize the police national database (PND) to carry out searches using historical face recognition. This procedure entails comparing a “probe image” of a person of interest against a database of over 19 million custody photos to identify possible hits.

Admitted Bias

The Home Office admitted last week that the system was biased. This admission came after a review by the National Physical Laboratory (NPL) determined it incorrectly matched people of Black and Asian heritage and women at much greater frequency than Caucasian males. The Home Office stated it “had acted on the findings”.

“It prompts the question of whether this technology only becomes useful if users accept biases in race and gender. Operational ease is a poor argument for overriding fundamental rights.”

Long-Standing Problem

Official papers show that this discriminatory flaw has been known about for more than a year. Furthermore, law enforcement lobbied to reverse an initial decision that was intended to mitigate the problem.

Senior officers were notified of the algorithmic discrimination in September 2024. The Home Office-commissioned NPL review found the system was had a higher probability to produce incorrect matches for images depicting females, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In response, the national police leadership body mandated that the accuracy setting required for possible hits be raised to a point where the disparity was significantly reduced.

However, this decision was overturned the following month following complaints from police that the modified technology was generating fewer “useful lines of inquiry”. Internal records show the higher threshold cut the number of queries that yielded potential matches from 56% to a just under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is currently used, the latest independent review discovered the system could generate incorrect matches for women of Black heritage nearly a hundred times more frequently than for Caucasian women at specific configurations.

The ministry commented on these findings: “Our evaluation identified that in a specific scenarios the algorithm is has a greater tendency to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's accuracy setting, the police records note: “The change greatly lessens the impact of discrimination across protected characteristics of race, generation and sex but had a substantially detrimental effect on operational effectiveness”. The documents add that police units complained that “a previously useful tool now delivered results of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a two-and-a-half-month consultation on its plans to widen the use of facial recognition technology. Policing minister Sarah Jones has described the tool as the “most significant advance since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the police race action plan, commented: “We observed scant consideration through equality strategy sessions of the technology deployment despite clear relevance with the strategy's goals.

“These revelations show once again that the pledges to combat discrimination policing has undertaken through the equality initiative are failing to be integrated into broader operations. Our reports have warned that innovative tools are being rolled out in a context where ethnic inequalities, weak scrutiny and faulty information gathering already persist.

“All deployment of this technology must adhere to strict national standards, be independently scrutinised, and demonstrate it diminishes rather than exacerbates racial disparity.”

Home Office Response

A Home Office spokesperson said: “The Home Office takes the conclusions of the report seriously and we have implemented changes. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be tested in the coming months and will be subject to further assessment.

“Our priority is protecting the public. This revolutionary tool will support police 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.”