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Police forces across the UK effectively campaigned to deploy a face scanning system known to be biased against women, young people, and members of ethnic minority groups, following complaints that a less biased version generated a reduced number of potential suspects.

How the System Works

UK forces utilize 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 database of more than 19 million custody photos to find potential matches.

Admitted Bias

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

“It prompts the issue of whether facial recognition only becomes useful if users accept biases in ethnicity and sex. Convenience is a weak argument for disregarding fundamental rights.”

Long-Standing Problem

Official papers show that this bias has been known about for over twelve months. Furthermore, law enforcement argued to overturn an initial decision that was intended to mitigate the problem.

Police bosses were informed of the algorithmic discrimination in late 2024. The Home Office-commissioned laboratory study concluded the system was had a higher probability to produce false positives for images depicting women, Black people, and those under 40 years old.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches be increased to a level where the disparity was greatly diminished.

However, this directive was overturned the following month after forces complained that the modified technology was producing a lower number of “useful lines of inquiry”. Internal records indicate the stricter setting reduced the number of queries that yielded potential matches from 56% to a mere 14%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold is currently used, the recent NPL study discovered the system could produce false positives for Black women almost 100 times more frequently than for Caucasian women at specific configurations.

The ministry stated on these findings: “Our evaluation identified that in a limited set of circumstances the software is has a greater tendency to wrongly flag some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Outlining the impact of the temporary raise to the system's confidence threshold, the police records state: “The change significantly reduces the effect of bias across protected characteristics of ethnicity, generation and gender but had a significant negative impact on police efficiency”. The documents add that forces argued that “a once effective tactic returned outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month consultation 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”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the advisory panel for the national policing equality strategy, said: “There was scant discussion through equality strategy sessions of the technology deployment even with clear relevance with the plan’s concerns.

“These revelations show once again that the pledges to combat discrimination policing has made via the equality initiative are failing to be integrated into wider practice. Our reports have warned that new technologies are being rolled out in a context where racial disparities, weak scrutiny and poor data collection continue to exist.

“Any use of facial recognition must meet rigorous official guidelines, be independently scrutinised, and demonstrate it reduces rather than compounds racial disparity.”

Official Statement

A Home Office spokesperson stated: “The Home Office takes the conclusions of the study seriously and we have implemented changes. A updated software has been externally evaluated and procured, which has no statistically significant bias. It will be trialled early next year and will be undergo further assessment.

“The foremost aim is ensuring public safety. This revolutionary tool will assist police to apprehend and prosecute offenders. There is officer review in every step of the procedure and no arrest or charge would be pursued without trained officers carefully reviewing the output.”