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Police forces across the United Kingdom effectively campaigned to use a facial recognition system known to be biased against women, young people, and members of ethnic minority groups, after complaining that a less biased version produced fewer investigative leads.

How the System Works

British police use the national police database to carry out retrospective facial recognition searches. This procedure involves matching a reference photograph of a suspect against a database of over 19 million mugshots to find possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the system was biased. This admission followed a study by the National Physical Laboratory (NPL) found it incorrectly matched people of Black and Asian heritage and females at much greater frequency than Caucasian males. The Home Office said it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes effective if users tolerate biases in race and gender. Convenience is a poor argument for disregarding basic freedoms.”

Known Issue

Internal documents reveal that this discriminatory flaw has been known about for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was intended to address the problem.

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

A Policy U-Turn

In reaction, the national police leadership body mandated that the accuracy setting required for potential matches be increased to a level where the bias was greatly diminished.

However, this directive was reversed the following month following complaints from police that the adjusted system was producing a lower number of “investigative leads”. Internal records show the stricter setting reduced the number of queries resulting in possible identifications from 56% to a mere under 15%.

Severe Disparities

Although the authorities refused to say what threshold is currently used, the latest independent review found the system could produce incorrect matches for Black women almost 100 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 more likely to incorrectly include some population segments in its match reports.”

Operational Effectiveness vs. Bias

Outlining the impact of the temporary raise to the system's confidence threshold, the police records note: “The change greatly lessens the impact of discrimination across legally safeguarded attributes of ethnicity, generation and sex but had a significant negative impact on police efficiency”. The documents further note that forces argued that “a once effective tactic returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a two-and-a-half-month public review on its plans to expand the use of facial recognition technology. The minister for police the relevant minister has described 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, commented: “We observed scant discussion in race action plan meetings of the technology deployment despite clear relevance with the plan’s concerns.

“This disclosure demonstrate once again that the anti-racism commitments the police has undertaken through the equality initiative are not being translated into broader operations. Our reports have warned that new technologies are being implemented in a context where racial disparities, inadequate oversight and poor data collection continue to exist.

“Any use of this technology must adhere to rigorous official guidelines, be subject to external review, and prove it diminishes rather than compounds racial disparity.”

Home Office Response

A government representative said: “The Home Office treat the conclusions of the study with utmost gravity and we have implemented changes. A new algorithm has been externally evaluated and acquired, which has no statistically significant bias. It will be trialled early next year and will be subject to evaluation.

“The foremost aim is ensuring public safety. This gamechanging technology will assist officers to apprehend and prosecute offenders. There is officer review in every step of the procedure and no further action would be pursued without trained officers carefully reviewing the results.”