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

How the System Works

UK forces use the police national database (PND) to carry out searches using historical face recognition. This procedure involves comparing a “probe image” of a suspect against a repository of over 19 million mugshots to find possible hits.

Admitted Bias

The UK interior ministry conceded last week that the system was flawed. This acknowledgment came after a review by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and females at much greater frequency than white men. The ministry said it “took steps on the findings”.

“This raises the question of whether facial recognition only becomes effective if users accept biases in ethnicity and sex. Operational ease is a weak argument for overriding basic freedoms.”

Long-Standing Problem

Internal documents show that this discriminatory flaw has been recognized for over twelve months. Furthermore, law enforcement argued to overturn an earlier ruling that was intended to address 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, Black people, and those aged 40 and under.

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 level where the bias was significantly reduced.

However, this directive was overturned the following month after forces complained that the adjusted system was generating a lower number of “useful lines of inquiry”. NPCC documents show the higher threshold reduced the number of searches resulting in possible identifications from over half to a just 14%.

Profound Inequalities

Although the Home Office and NPCC declined to specify what threshold is now in operation, the recent NPL study found the system could generate false positives for women of Black heritage almost 100 times more often than for Caucasian women at specific configurations.

The Home Office stated on these findings: “Our evaluation identified that in a specific scenarios the software is has a greater tendency to incorrectly include some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Describing the effect of the brief increase to the system's accuracy setting, the police records state: “The change greatly lessens the effect of bias across protected characteristics of ethnicity, generation and sex but had a substantially detrimental effect on operational effectiveness”. The documents further note that police units complained that “a once effective tactic now delivered outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a ten-week public review on its proposals to expand the use of facial recognition technology. Policing minister the relevant minister has described the tool as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “There was scant consideration through equality strategy sessions of the technology deployment despite obvious cross-over with the strategy's goals.

“This disclosure demonstrate yet again that the pledges to combat discrimination policing has made via the equality initiative are failing to be integrated into broader operations. Our reports have warned that new technologies are being implemented in a landscape where racial disparities, inadequate oversight and faulty information gathering continue to exist.

“All deployment of facial recognition must meet rigorous official guidelines, be subject to external review, and prove it diminishes rather than compounds racial disparity.”

Home Office Response

A Home Office spokesperson stated: “The Home Office takes the findings of the report seriously and we have already taken action. A new algorithm has been independently tested and procured, which has demonstrated no measurable discrimination. It will be tested in the coming months and will be undergo further assessment.

“Our priority is protecting the public. This gamechanging technology will support police to apprehend and prosecute offenders. There is human involvement in each stage of the procedure and no arrest or charge would be pursued without trained officers carefully reviewing the results.”