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Law enforcement agencies across the United Kingdom effectively campaigned to use a facial recognition system known to be biased against women, youths, and members of ethnic minority groups, after complaining that a more accurate version generated fewer potential suspects.

How the System Works

British police use the police national database (PND) to carry out retrospective facial recognition searches. This process involves matching a reference photograph of a suspect against a repository of over 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office admitted last week that the system was biased. This acknowledgment followed a study by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and women at significantly higher rates than Caucasian males. The Home Office stated it “had acted on the findings”.

“This raises the issue of whether this technology only becomes useful if users tolerate biases in ethnicity and gender. Operational ease is a weak argument for disregarding fundamental rights.”

Known Issue

Official papers show that this discriminatory flaw has been known about for over twelve months. Furthermore, law enforcement lobbied to reverse an initial decision that was designed to mitigate the problem.

Police bosses were notified of the algorithmic discrimination in September 2024. The government-ordered laboratory study found the system was more likely to produce false positives for photos of women, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

In response, the national police leadership body mandated that the accuracy setting required for potential matches be increased to a point where the disparity was significantly reduced.

However, this decision was reversed the following month after forces complained that the modified technology was producing a lower number of “investigative leads”. Internal records show the higher threshold cut the proportion of searches that yielded possible identifications from over half to a just under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what setting is now in operation, the recent independent review found the system could generate incorrect matches for Black women nearly a hundred times more often than for Caucasian women at specific configurations.

The Home Office stated on these findings: “Our evaluation identified that in a limited set of circumstances the algorithm is has a greater tendency to incorrectly include some population segments in its search results.”

Operational Effectiveness vs. Bias

Outlining the effect of the temporary raise to the system's accuracy setting, the police records note: “The change significantly reduces the impact of bias across legally safeguarded attributes of race, generation and sex but had a significant negative impact on operational effectiveness”. The documents further note that forces complained that “a previously useful tool now delivered results of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a ten-week public review on its plans to expand the use of biometric scanning systems. Policing minister the relevant minister has described the technology as the “biggest breakthrough since genetic fingerprinting”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the advisory panel for the police race action plan, said: “We observed very little discussion in race action plan meetings of the technology deployment despite clear relevance with the strategy's goals.

“These revelations show once again that the anti-racism commitments the police has undertaken through the equality initiative are not being translated into broader operations. Independent assessments have cautioned that new technologies are being implemented in a context where racial disparities, inadequate oversight and faulty information gathering already persist.

“Any use of this technology must meet strict national standards, be independently scrutinised, and prove it diminishes rather than compounds ethnic bias.”

Home Office Response

A Home Office spokesperson stated: “The Home Office takes the findings of the study seriously and we have already taken action. A new algorithm has been externally evaluated and procured, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be subject to evaluation.

“Our priority is ensuring public safety. This revolutionary tool will support officers to put criminals and rapists behind bars. There is officer review in each stage of the process and no arrest or charge would be pursued without trained officers carefully reviewing the output.”