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Law enforcement agencies across the UK successfully lobbied to use a face scanning system acknowledged as discriminatory against females, youths, and members of ethnic minority groups, following complaints that a less biased version produced a reduced number of potential suspects.

How the System Works

British police use the police national database (PND) to carry out searches using historical face recognition. This process entails matching a “probe image” of a suspect against a database of over 19 million mugshots to identify potential matches.

Admitted Bias

The UK interior ministry admitted last week that the system was flawed. This admission followed a review by the government's National Physical Laboratory found it misidentified people of Black and Asian heritage and women at much greater frequency than white men. The ministry said it “had acted on the findings”.

“This raises the issue of whether this technology only becomes useful if users tolerate biases in ethnicity and sex. Convenience is a weak argument for overriding basic freedoms.”

Known Issue

Official papers reveal that this bias has been known about for more than a year. Furthermore, law enforcement argued to overturn an initial decision that was intended to address the problem.

Police bosses were notified of the system's bias in September 2024. The Home Office-commissioned NPL review concluded the system was had a higher probability to suggest incorrect matches for photos of females, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

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

However, this directive was reversed the next month following complaints from police that the modified technology was generating a lower number of “investigative leads”. NPCC documents show the stricter setting reduced the number of searches resulting in potential matches from over half to a just under 15%.

Severe Disparities

Although the authorities refused to say what threshold is now in operation, the latest independent review discovered the system could generate false positives for women of Black heritage nearly a hundred times more frequently than for white women at specific configurations.

The ministry commented on these findings: “Our evaluation found that in a limited set of circumstances the algorithm is has a greater tendency to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's accuracy setting, the police records note: “The change significantly reduces the effect of discrimination across protected characteristics of race, generation and gender but had a significant negative impact on police efficiency”. The papers further note that forces complained that “a previously useful tool now delivered results of questionable value”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month consultation on its plans to widen the use of biometric scanning systems. The minister for police Sarah Jones has labeled the tool as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the police race action plan, commented: “There was very little consideration through equality strategy sessions of the facial recognition rollout despite obvious cross-over with the strategy's goals.

“This disclosure demonstrate yet again that the anti-racism commitments policing has made via the equality initiative are not being translated into wider practice. Our reports have cautioned that new technologies are being implemented in a context where racial disparities, weak scrutiny and faulty information gathering already persist.

“Any use of this technology must adhere to strict national standards, be independently scrutinised, and prove it diminishes rather than exacerbates racial disparity.”

Home Office Response

A government representative stated: “The Home Office treat the conclusions of the report with utmost gravity and we have already taken action. A new algorithm has been independently tested and acquired, which has no statistically significant bias. It will be tested early next year and will be undergo further assessment.

“Our priority is protecting the public. This gamechanging technology will assist officers to apprehend and prosecute offenders. There is human involvement in each stage of the process and no arrest or charge would be taken without specialist personnel carefully reviewing the output.”