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Police forces across the UK successfully lobbied to deploy a facial recognition system known to be biased against females, youths, and individuals from minority ethnic backgrounds, after complaining that a less biased version produced a reduced number of investigative leads.

The Technology in Practice

British police use the police national database (PND) to conduct retrospective facial recognition searches. This process involves comparing a reference photograph of a person of interest against a database of over 19 million mugshots to find possible hits.

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) found it misidentified people of Black and Asian heritage and females at significantly higher rates than white men. The Home Office stated it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes effective if users tolerate biases in race and sex. Operational ease is a weak argument for overriding fundamental rights.”

Long-Standing Problem

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

Senior officers were informed of the algorithmic discrimination in September 2024. The government-ordered laboratory study concluded the system was more likely to suggest incorrect matches 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 accuracy setting required for potential matches be raised to a point where the bias was significantly reduced.

However, this directive was reversed the next month following complaints from police that the modified technology was producing a lower number of “useful lines of inquiry”. NPCC documents show the higher threshold reduced the number of searches that yielded potential matches from 56% to a just under 15%.

Severe Disparities

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

The ministry stated on these results: “The testing identified that in a limited set of circumstances the algorithm is more likely to incorrectly include some demographic groups in its search results.”

Balancing Utility and Fairness

Outlining the effect of the brief increase to the system's confidence threshold, the police records state: “This adjustment significantly reduces the effect of discrimination across legally safeguarded attributes of race, generation and sex but had a substantially detrimental effect on police efficiency”. The papers add that police units complained that “a once effective tactic returned results of questionable value”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a two-and-a-half-month 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 genetic fingerprinting”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “We observed very little discussion through equality strategy sessions of the technology deployment despite clear relevance with the plan’s concerns.

“This disclosure demonstrate once again that the anti-racism commitments policing has made through the equality initiative are failing to be integrated into broader operations. Our reports have warned that innovative tools are being rolled out in a context where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

“Any use of facial recognition must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than exacerbates ethnic bias.”

Official Statement

A Home Office spokesperson stated: “The Home Office treat the findings of the report seriously and we have already taken action. A updated software has been independently tested and procured, which has no statistically significant bias. 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 apprehend and prosecute offenders. There is officer review in each stage of the process and no arrest or charge would be pursued without specialist personnel carefully reviewing the output.”