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Police forces across the United Kingdom effectively campaigned to use a face scanning system acknowledged as biased against females, youths, and individuals from minority ethnic backgrounds, after complaining that a less biased version produced fewer potential suspects.

How the System Works

UK forces use the police national database (PND) to conduct searches using historical face recognition. This process involves matching a “probe image” of a person of interest against a repository of over 19 million mugshots to identify potential matches.

Acknowledged Discrimination

The Home Office conceded last week that the system was flawed. This acknowledgment followed a review by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and women at significantly higher rates than white men. The ministry stated it “had acted on the findings”.

“It prompts the question of whether this technology only becomes useful if users accept discrimination in ethnicity and sex. Operational ease is a weak argument for disregarding basic freedoms.”

Long-Standing Problem

Internal documents reveal 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 address the problem.

Senior officers were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study found the system was more likely to suggest false positives 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 confidence threshold required for possible hits be raised to a point where the bias was significantly reduced.

However, this directive was overturned the next month after forces complained that the modified technology was generating fewer “investigative leads”. Internal records indicate the stricter setting reduced the proportion of queries resulting in possible identifications from 56% to a just 14%.

Profound Inequalities

Although the authorities refused to say what threshold is now in operation, the latest NPL study found the system could produce false positives for women of Black heritage nearly a hundred times more frequently than for white women at certain settings.

The ministry commented on these findings: “The testing found that in a specific scenarios the algorithm is more likely to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the impact of the brief increase to the system's confidence threshold, the NPCC documents note: “This adjustment significantly reduces the effect of discrimination across protected characteristics of race, age and gender but had a substantially detrimental effect on police efficiency”. The papers further note that forces argued that “a once effective tactic now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has launched a two-and-a-half-month public review on its proposals to expand the use of biometric scanning systems. The minister for police Sarah Jones has labeled the tool as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the police race action plan, commented: “There was very little consideration in race action plan meetings of the facial recognition rollout even with clear relevance with the strategy's goals.

“This disclosure show yet again that the pledges to combat discrimination policing has undertaken via the equality initiative are failing to be integrated into broader operations. Our reports have cautioned that new technologies are being rolled out in a context where racial disparities, inadequate oversight and poor data collection continue to exist.

“All deployment of facial recognition must meet strict national standards, be subject to external review, and prove it diminishes rather than exacerbates racial disparity.”

Home Office Response

A Home Office spokesperson stated: “We treat the conclusions of the report seriously and we have already taken action. A new algorithm has been externally evaluated and acquired, which has no statistically significant bias. It will be tested early next year and will be subject to evaluation.

“The foremost aim is ensuring public safety. This revolutionary tool will assist police to apprehend and prosecute offenders. There is human involvement in each stage of the process and no arrest or charge would be pursued without trained officers meticulously examining the results.”