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Police forces across the United Kingdom effectively campaigned to use a face scanning system known to be biased against females, young people, and individuals from minority ethnic backgrounds, following complaints that a less biased version generated a reduced number of investigative leads.

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 person of interest against a repository of more than 19 million custody photos to identify potential matches.

Acknowledged Discrimination

The Home Office admitted last week that the technology was flawed. This acknowledgment followed a study by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and women at significantly higher rates than white men. The Home Office said it “had acted on the findings”.

“It prompts the issue of whether this technology only becomes effective if users accept discrimination in ethnicity and sex. Convenience is a poor argument for disregarding basic freedoms.”

Known Issue

Internal documents show that this discriminatory flaw has been recognized for more than a year. Furthermore, law enforcement lobbied to reverse an initial decision that was designed to mitigate the problem.

Senior officers were informed of the system's bias in late 2024. The government-ordered laboratory study concluded the system was more likely to produce incorrect matches for photos of women, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for potential matches be increased to a level where the disparity was greatly diminished.

However, this decision was overturned the following month after forces complained that the adjusted system was producing a lower number of “investigative leads”. NPCC documents show the higher threshold reduced the number of queries resulting in potential matches from 56% to a mere under 15%.

Profound Inequalities

Although the authorities declined to specify what threshold is now in operation, the recent NPL study discovered the system could produce false positives for Black women almost 100 times more often than for white women at specific configurations.

The ministry stated on these results: “The testing found that in a limited set of circumstances the algorithm is more likely to wrongly flag some population segments in its search results.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents state: “The change significantly reduces the impact of discrimination across legally safeguarded attributes of race, age and sex but had a significant negative impact on police efficiency”. The documents add that police units argued that “a once effective tactic returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week public review on its proposals to widen the use of facial recognition technology. Policing minister Sarah Jones has labeled the tool as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the advisory panel for the national policing equality strategy, said: “There was very little discussion through equality strategy sessions of the facial recognition rollout despite obvious cross-over with the strategy's goals.

“These revelations show yet again that the anti-racism commitments the police has undertaken through the equality initiative are failing to be integrated into wider practice. Our reports have warned that innovative tools are being implemented in a context where racial disparities, weak scrutiny and poor data collection already persist.

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

Official Statement

A government representative stated: “We takes the findings of the report with utmost gravity and we have already taken action. A new algorithm has been independently tested and procured, which has demonstrated no measurable discrimination. It will be tested in the coming months and will be subject to further assessment.

“Our priority is protecting the public. 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 further action would be pursued without trained officers carefully reviewing the output.”