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Law enforcement agencies across the United Kingdom effectively campaigned to deploy a face scanning system known to be biased against females, young people, and members of minority ethnic backgrounds, following complaints that a less biased version generated a reduced number of potential suspects.

The Technology in Practice

UK forces use the police national database (PND) to carry out retrospective facial recognition searches. This process involves comparing a reference photograph of a suspect against a repository of over 19 million mugshots to identify possible hits.

Admitted Bias

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

“This raises the issue of whether facial recognition only becomes useful if users accept discrimination in ethnicity and gender. Convenience is a poor argument for disregarding fundamental rights.”

Known Issue

Official papers show that this bias has been recognized for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was designed to mitigate the problem.

Senior officers were informed of the algorithmic discrimination in late 2024. The Home Office-commissioned NPL review found the system was had a higher probability to suggest false positives for photos of females, Black people, and those under 40 years old.

A Reversed Decision

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

However, this directive was reversed the following month following complaints from police that the modified technology was generating a lower number of “investigative leads”. NPCC documents show the higher threshold reduced the proportion of searches that yielded possible identifications from 56% to a mere under 15%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold is currently used, the recent independent review discovered the system could produce false positives for women of Black heritage nearly a hundred times more often than for white women at specific configurations.

The Home Office stated on these results: “Our evaluation identified that in a limited set of circumstances the software is has a greater tendency to incorrectly include some demographic groups in its match reports.”

Balancing Utility and Fairness

Describing the effect of the brief increase to the system's accuracy setting, the NPCC documents state: “This adjustment significantly reduces the effect of bias across protected characteristics of ethnicity, age and gender but had a significant negative impact on police efficiency”. The papers further note that forces complained that “a previously useful tool returned outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week consultation on its plans to widen the use of facial recognition technology. Policing minister Sarah Jones has described the technology as the “biggest breakthrough since genetic fingerprinting”.

Expert and Oversight Concerns

Abimbola Johnson, head of the independent scrutiny and oversight board for the police race action plan, said: “There was very little discussion through race action plan meetings of the facial recognition rollout even with obvious cross-over with the plan’s concerns.

“This disclosure show yet again that the pledges to combat discrimination the police has undertaken via the race action plan are not being translated into wider practice. Independent assessments have warned that innovative tools are being implemented in a context where racial disparities, inadequate oversight and faulty information gathering already persist.

“All deployment of this technology must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it reduces rather than compounds ethnic bias.”

Home Office Response

A government representative stated: “We treat the conclusions of the study seriously and we have already taken action. A updated software has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be trialled early next year and will be subject to evaluation.

“The foremost aim is protecting the public. This gamechanging technology will support officers to apprehend and prosecute offenders. There is human involvement in each stage of the procedure and no arrest or charge would be pursued without specialist personnel carefully reviewing the output.”