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Police forces across the United Kingdom successfully lobbied to deploy a face scanning system known to be biased against females, youths, and members of ethnic minority groups, after complaining that a less biased version produced fewer investigative leads.

The Technology in Practice

UK forces utilize the national police database to conduct retrospective facial recognition searches. This procedure involves matching a “probe image” of a person of interest against a database of over 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office admitted last week that the technology was flawed. This admission came after a study by the National Physical Laboratory (NPL) determined it misidentified people of Black and Asian heritage and women at significantly higher rates than white men. The ministry said it “had acted on the findings”.

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

Long-Standing Problem

Official papers show that this bias has been recognized for over twelve months. Furthermore, police forces argued to overturn an earlier ruling 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 false positives for images depicting females, Black people, and those aged 40 and under.

A Reversed Decision

In reaction, the national police leadership body mandated that the confidence threshold required for potential matches be raised to a point where the bias was significantly reduced.

However, this decision was overturned the following month following complaints from police that the adjusted system was producing fewer “investigative leads”. NPCC documents show the higher threshold reduced the proportion of queries resulting in possible identifications from 56% to a just under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what setting is currently used, the latest NPL study discovered the system could generate 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: “Our evaluation found that in a limited set of circumstances the algorithm is has a greater tendency to wrongly flag some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Describing the effect of the temporary raise to the system's confidence threshold, the police records state: “This adjustment significantly reduces the effect of bias across protected characteristics of race, generation and gender but had a substantially detrimental effect on police efficiency”. The documents add that forces complained that “a once effective tactic returned outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a ten-week public review on its proposals to widen the use of biometric scanning systems. Policing minister Sarah Jones has described the tool as the “biggest breakthrough since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, head of the advisory panel for the police race action plan, commented: “There was very little discussion through race action plan meetings of the facial recognition rollout even with clear relevance with the plan’s concerns.

“This disclosure show once again that the anti-racism commitments the police has undertaken through the race action plan are failing to be integrated into wider practice. Our reports have warned that innovative tools are being implemented in a context where racial disparities, inadequate oversight and poor data collection already persist.

“Any use of facial recognition must adhere to strict national standards, be subject to external review, and prove it diminishes rather than compounds ethnic bias.”

Home Office Response

A Home Office spokesperson said: “We 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 trialled early next year and will be subject to further assessment.

“Our priority is protecting the public. This gamechanging technology will assist officers to apprehend and prosecute offenders. There is human involvement in each stage of the process and no further action would be pursued without trained officers meticulously examining the results.”