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Law enforcement agencies across the UK successfully lobbied to use a facial recognition system acknowledged as discriminatory against women, youths, and individuals from ethnic minority groups, following complaints that a more accurate version produced fewer potential suspects.

How the System Works

British police use the national police database to conduct retrospective facial recognition searches. This process entails comparing a “probe image” of a suspect against a repository of more than 19 million mugshots to find possible hits.

Admitted Bias

The Home Office conceded last week that the system was biased. This admission came after a study by the National Physical Laboratory (NPL) found it incorrectly matched people of Black and Asian heritage and women at much greater frequency than Caucasian males. The Home Office said it “took steps 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 poor argument for overriding basic freedoms.”

Known Issue

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 address the problem.

Police bosses were notified of the system's bias in late 2024. The Home Office-commissioned NPL review found the system was had a higher probability to suggest false positives for photos of females, Black people, 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 point where the bias was greatly diminished.

However, this directive was reversed the next month after forces complained that the modified technology was producing fewer “investigative leads”. NPCC documents indicate the higher threshold cut the proportion of queries resulting in potential matches from over half to a just under 15%.

Profound Inequalities

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

The Home Office commented 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.”

Balancing Utility and Fairness

Describing the impact of the temporary raise to the system's confidence threshold, the NPCC documents state: “This adjustment greatly lessens the effect of bias across legally safeguarded attributes of race, age and gender but had a significant negative impact on operational effectiveness”. The papers add that police units complained that “a previously useful tool returned results of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has opened a two-and-a-half-month public review on its plans to expand the use of biometric scanning systems. The minister for police the relevant minister has labeled the tool as the “biggest breakthrough since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the national policing equality strategy, said: “We observed very little consideration in race action plan meetings of the technology deployment even with clear relevance with the strategy's goals.

“This disclosure show once again that the anti-racism commitments policing has made via the race action plan are failing to be integrated into wider practice. Our reports have cautioned that new technologies are being implemented in a landscape where ethnic inequalities, inadequate oversight and poor data collection already persist.

“All deployment of this technology must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than exacerbates ethnic bias.”

Home Office Response

A government representative said: “The Home Office takes the findings of the report with utmost gravity and we have already taken action. A new algorithm has been externally evaluated and procured, which has demonstrated no measurable discrimination. It will be tested early next year and will be undergo further assessment.

“The foremost aim is protecting the public. This gamechanging technology will assist officers to apprehend and prosecute offenders. There is officer review in each stage of the procedure and no arrest or charge would be pursued without specialist personnel carefully reviewing the output.”