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Police forces across the United Kingdom effectively campaigned to deploy a face scanning system known to be biased against women, youths, and individuals from minority ethnic backgrounds, following complaints that a less biased version generated fewer investigative leads.

The Technology in Practice

UK forces use the national police database to conduct retrospective facial recognition searches. This procedure entails matching a “probe image” of a person of interest against a database of more than 19 million mugshots to find possible hits.

Admitted Bias

The Home Office admitted last week that the system was biased. This acknowledgment followed a study by the government's National Physical Laboratory found it incorrectly matched people of Black and Asian heritage and women at much greater frequency than Caucasian males. The Home Office stated it “had acted on the findings”.

“It prompts the question of whether facial recognition only becomes effective if users accept discrimination in race and gender. Operational ease is a poor argument for disregarding fundamental rights.”

Known Issue

Internal documents reveal that this discriminatory flaw has been known about for over twelve months. Furthermore, police forces argued to overturn an initial decision that was intended to mitigate the problem.

Senior officers were notified of the algorithmic discrimination in September 2024. The government-ordered NPL review found the system was had a higher probability to produce false positives for images depicting females, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In reaction, the national police leadership body ordered that the accuracy setting required for potential matches be raised to a level where the disparity was significantly reduced.

However, this directive was reversed the following month following complaints from police that the adjusted system was generating a lower number of “useful lines of inquiry”. Internal records indicate the stricter setting reduced the proportion of queries that yielded possible identifications from over half to a just 14%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is currently used, the latest NPL study discovered the system could generate false positives for Black women almost 100 times more often than for white women at specific configurations.

The ministry commented on these findings: “The testing found 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 effect of the temporary raise to the system's accuracy setting, the NPCC documents note: “The change greatly lessens the effect of bias across legally safeguarded attributes of ethnicity, generation and sex but had a significant negative impact on police efficiency”. The documents add that police units complained that “a once effective tactic now delivered results of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month 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

Abimbola Johnson, head of the advisory panel for the national policing equality strategy, commented: “There was scant discussion in race action plan meetings of the technology deployment even with clear relevance with the strategy's goals.

“These revelations show yet again that the anti-racism commitments the police has undertaken through the race action plan are not being translated into broader operations. Our reports have cautioned that innovative tools are being implemented in a landscape where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

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

Home Office Response

A Home Office spokesperson said: “We treat the findings of the study with utmost gravity and we have implemented changes. A new algorithm has been independently tested and acquired, which has demonstrated no measurable discrimination. It will be tested in the coming months and will be undergo evaluation.

“The foremost aim is ensuring public safety. This revolutionary tool will assist police to put criminals and rapists behind bars. There is officer review in each stage of the procedure and no further action would be taken without specialist personnel carefully reviewing the results.”