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

How the System Works

UK forces use the police national database (PND) to conduct retrospective facial recognition searches. This procedure involves matching a reference photograph of a suspect against a database of more than 19 million custody photos to find possible hits.

Acknowledged Discrimination

The UK interior ministry admitted last week that the technology was flawed. This admission came after a study by the National Physical Laboratory (NPL) determined it incorrectly matched people of Black and Asian heritage and females at much greater frequency than Caucasian males. The ministry stated it “took steps on the findings”.

“It prompts the issue of whether this technology only becomes useful if users tolerate discrimination in race and gender. Operational ease is a weak argument for disregarding fundamental rights.”

Known Issue

Internal documents show that this bias has been known about for more than a year. Furthermore, police forces lobbied to reverse an initial decision that was intended to mitigate the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study found the system was more likely to produce false positives for images depicting females, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for possible hits be increased to a point where the disparity was significantly reduced.

However, this decision was overturned the next month following complaints from police that the modified technology was producing a lower number of “investigative leads”. NPCC documents show the higher threshold cut the proportion of searches that yielded potential matches from 56% to a mere under 15%.

Severe Disparities

Although the authorities declined to specify what setting is currently used, the recent independent review found the system could produce false positives for women of Black heritage almost 100 times more often than for white women at specific configurations.

The Home Office commented on these findings: “Our evaluation found that in a specific scenarios the software is has a greater tendency to wrongly flag some population segments in its search results.”

Balancing Utility and Fairness

Describing the impact of the brief increase to the system's accuracy setting, the NPCC documents note: “This adjustment greatly lessens the effect of discrimination across legally safeguarded attributes of ethnicity, age and gender but had a substantially detrimental effect on operational effectiveness”. The papers further note that forces argued that “a previously useful tool now delivered outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week consultation on its plans to widen the use of biometric scanning systems. Policing minister Sarah Jones has described the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the advisory panel for the national policing equality strategy, said: “There was scant consideration through race action plan meetings of the facial recognition rollout even with clear relevance with the plan’s concerns.

“This disclosure demonstrate yet again that the pledges to combat discrimination the police has made via the equality initiative are failing to be integrated into broader operations. Independent assessments have cautioned that new technologies are being implemented in a context where ethnic inequalities, weak scrutiny and faulty information gathering already persist.

“All deployment of this technology must meet rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than exacerbates racial disparity.”

Home Office Response

A Home Office spokesperson said: “The Home Office treat the conclusions of the report seriously and we have implemented changes. A updated software has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be tested early next year and will be subject to evaluation.

“The foremost aim is protecting the public. This gamechanging technology will assist police to put criminals and rapists behind bars. There is officer review in every step of the process and no further action would be taken without specialist personnel carefully reviewing the output.”