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Law enforcement agencies across the United Kingdom effectively campaigned to deploy a face scanning system acknowledged as biased against females, young people, and individuals from ethnic minority groups, following complaints that a more accurate version produced fewer potential suspects.

The Technology in Practice

British police use the police national database (PND) to conduct retrospective facial recognition searches. This procedure entails matching a reference photograph of a person of interest against a database of more than 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office conceded last week that the system was flawed. This admission 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 Caucasian males. The ministry stated it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users accept biases in ethnicity and sex. Operational ease is a weak argument for overriding 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 designed to mitigate the problem.

Police bosses were informed of the system's bias in late 2024. The Home Office-commissioned laboratory study found the system was more likely to suggest false positives for images depicting females, Black people, and those under 40 years old.

A Policy U-Turn

In reaction, the national police leadership body ordered that the confidence threshold required for potential matches be increased to a level where the disparity was greatly diminished.

However, this directive was reversed the following month after forces complained that the adjusted system was generating fewer “useful lines of inquiry”. Internal records indicate the higher threshold reduced the number of queries resulting in potential matches from over half to a mere 14%.

Profound Inequalities

Although the authorities refused to say what setting is now in operation, the recent NPL study discovered the system could generate incorrect matches for women of Black heritage nearly a hundred times more frequently than for Caucasian 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 incorrectly include some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Outlining the effect of the temporary raise to the system's confidence threshold, the NPCC documents note: “This adjustment significantly reduces the impact of discrimination across legally safeguarded attributes of ethnicity, age and sex but had a significant negative impact on police efficiency”. The documents add that police units complained that “a previously useful tool returned results of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has opened a two-and-a-half-month consultation on its plans to expand the use of biometric scanning systems. Policing minister Sarah Jones has described the technology as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the advisory panel for the police race action plan, said: “There was very little consideration in race action plan meetings of the facial recognition rollout despite clear relevance with the plan’s concerns.

“These revelations show once again that the anti-racism commitments the police has undertaken via the race action plan are not being translated into wider practice. Independent assessments have cautioned that innovative tools are being rolled out in a landscape where ethnic inequalities, weak scrutiny and poor data collection continue to exist.

“Any use of facial recognition must meet rigorous official guidelines, be independently scrutinised, and prove it reduces 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 new algorithm has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be subject to evaluation.

“Our priority is protecting the public. This gamechanging technology will assist officers to put criminals and rapists behind bars. There is officer review in each stage of the procedure and no further action would be pursued without specialist personnel meticulously examining the results.”