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Police forces across the United Kingdom successfully lobbied to deploy a facial recognition system known to be biased against females, young people, and members of minority ethnic backgrounds, following complaints that a less biased version produced fewer potential suspects.

The Technology in Practice

British police utilize the national police database to conduct searches using historical face recognition. This procedure involves matching a “probe image” of a person of interest against a repository of over 19 million mugshots to find possible hits.

Admitted Bias

The UK interior ministry conceded last week that the technology was biased. This admission followed a review by the National Physical Laboratory (NPL) found it incorrectly matched people of Black and Asian heritage and females at significantly higher rates than white men. The ministry said it “took steps on the findings”.

“It prompts the issue of whether this technology only becomes effective if users tolerate biases in race and gender. Operational ease is a weak argument for overriding fundamental rights.”

Long-Standing Problem

Internal documents show that this discriminatory flaw has been known about for over twelve months. Furthermore, police forces lobbied to reverse an initial decision that was designed to address the problem.

Senior officers were notified of the algorithmic discrimination in late 2024. The government-ordered NPL review found the system was more likely to suggest false positives for images depicting women, Black people, and those aged 40 and under.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for potential matches be increased to a point where the bias was significantly reduced.

However, this decision was reversed the following month following complaints from police that the adjusted system was producing fewer “investigative leads”. NPCC documents indicate the higher threshold cut the number of queries that yielded potential matches from over half to a just 14%.

Profound Inequalities

Although the authorities declined to specify what threshold is now in operation, the latest NPL study found the system could produce incorrect matches for Black women nearly a hundred times more often than for white women at specific configurations.

The Home Office stated on these findings: “The testing identified that in a specific scenarios the algorithm is has a greater tendency to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the impact of the brief increase to the system's confidence threshold, the NPCC documents state: “The change significantly reduces the impact of discrimination across protected characteristics of race, age and gender but had a significant negative impact on police efficiency”. The documents further note that police units complained that “a once effective tactic returned outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a ten-week consultation on its proposals to widen the use of facial recognition technology. The minister for police the relevant minister has described the technology as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the independent scrutiny and oversight board for the national policing equality strategy, said: “We observed very little consideration in race action plan meetings of the facial recognition rollout even with 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 new technologies are being implemented in a landscape where ethnic inequalities, weak scrutiny and faulty information gathering continue to exist.

“Any use of facial recognition must adhere to strict national standards, be subject to external review, and prove it reduces rather than exacerbates ethnic bias.”

Home Office Response

A government representative stated: “We takes the conclusions of the report with utmost gravity and we have implemented changes. A new algorithm has been externally evaluated and procured, which has demonstrated no measurable discrimination. It will be trialled early next year and will be subject to further assessment.

“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 process and no arrest or charge would be pursued without trained officers carefully reviewing the results.”