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Police forces across the UK effectively campaigned to use a face scanning system acknowledged as discriminatory against females, youths, and members of minority ethnic backgrounds, after complaining that a less biased version generated a reduced number of investigative leads.

The Technology in Practice

UK forces utilize the police national database (PND) to carry out retrospective facial recognition searches. This process entails comparing a “probe image” of a person of interest against a database of more than 19 million mugshots to find potential matches.

Admitted Bias

The UK interior ministry admitted last week that the system was biased. This acknowledgment came after a review by the government's National Physical Laboratory found it misidentified people of Black and Asian heritage and females at significantly higher rates than white men. The Home Office stated it “had acted on the findings”.

“This raises the question of whether facial recognition only becomes useful if users accept discrimination in race and sex. Operational ease is a weak argument for disregarding fundamental rights.”

Known Issue

Official papers show that this bias has been recognized for more than a year. Furthermore, police forces argued to overturn an initial decision that was intended to mitigate the problem.

Senior officers were informed of the system's bias in late 2024. The Home Office-commissioned laboratory study concluded the system was more likely to suggest false positives for images depicting females, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

In response, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for possible hits be raised to a level where the disparity was significantly reduced.

However, this decision was overturned the next month after forces complained that the modified technology was producing a lower number of “investigative leads”. NPCC documents indicate the higher threshold cut the proportion of queries that yielded potential matches from over half to a mere 14%.

Profound Inequalities

Although the authorities refused to say what threshold is currently used, the latest independent review found the system could produce false positives for Black women almost 100 times more often than for white women at specific configurations.

The Home Office commented on these findings: “Our evaluation found that in a limited set of circumstances the software is more likely to wrongly flag some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Outlining the effect of the brief increase to the system's accuracy setting, the NPCC documents note: “The change greatly lessens the impact of discrimination across legally safeguarded attributes of race, age and sex but had a substantially detrimental effect on operational effectiveness”. The papers further note that forces complained that “a once effective tactic returned outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the government has launched 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 described the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the independent scrutiny and oversight board for the police race action plan, said: “There was scant consideration through race action plan meetings of the facial recognition rollout even with obvious cross-over with the plan’s concerns.

“These revelations show once again that the anti-racism commitments policing has made through the race action plan are failing to be integrated into wider practice. Independent assessments have warned that innovative tools are being implemented in a landscape where ethnic inequalities, inadequate oversight and poor data collection continue to exist.

“All deployment of this technology must meet rigorous official guidelines, be subject to external review, and demonstrate it diminishes rather than compounds ethnic bias.”

Official Statement

A government representative said: “The Home Office takes the conclusions of the report with utmost gravity and we have implemented changes. A updated software 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.

“The foremost aim is protecting the public. This gamechanging technology will support officers to apprehend and prosecute offenders. There is officer review in each stage of the procedure and no further action would be pursued without specialist personnel meticulously examining the output.”