🔗 Share this article

Police forces across the United Kingdom effectively campaigned to deploy a face scanning system acknowledged as biased against females, young people, and members of ethnic minority groups, after complaining that a more accurate version generated fewer potential suspects.

How the System Works

British police use the police national database (PND) to carry out retrospective facial recognition searches. This procedure entails matching a “probe image” of a suspect against a database of over 19 million mugshots to find potential matches.

Admitted Bias

The UK interior ministry admitted last week that the technology was biased. This acknowledgment came after a study by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and females at significantly higher rates than white men. The Home Office said it “had acted on the findings”.

“This raises the question of whether this technology only becomes useful if users accept discrimination in ethnicity and sex. Convenience is a weak argument for disregarding fundamental rights.”

Known Issue

Official papers show that this discriminatory flaw has been known about for over twelve months. Furthermore, police forces argued to overturn an earlier ruling that was designed to address the problem.

Police bosses were notified of the system's bias in late 2024. The government-ordered NPL review found the system was more likely to suggest false positives for images depicting women, Black people, and those aged 40 and under.

A Policy U-Turn

In response, the National Police Chiefs’ Council (NPCC) mandated that the accuracy setting required for potential matches be raised to a point where the bias was greatly diminished.

However, this decision was overturned the next month following complaints from police that the adjusted system was generating fewer “useful lines of inquiry”. NPCC documents show the stricter setting reduced the number of queries that yielded possible identifications from 56% to a just under 15%.

Profound Inequalities

Although the authorities declined to specify what threshold is currently used, the latest independent review discovered the system could generate incorrect matches for Black women almost 100 times more often than for Caucasian women at specific configurations.

The ministry stated on these findings: “The testing identified that in a limited set of circumstances the software is more likely to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the impact of the brief increase to the system's confidence threshold, the police records note: “This adjustment greatly lessens the impact of bias across legally safeguarded attributes of ethnicity, generation and gender but had a substantially detrimental effect on operational effectiveness”. The documents add that forces complained that “a previously useful tool now delivered results of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has launched a two-and-a-half-month consultation on its proposals to widen the use of biometric scanning systems. Policing minister Sarah Jones has described the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the advisory panel for the police race action plan, commented: “We observed very little consideration through equality strategy sessions of the technology deployment even with obvious cross-over with the strategy's goals.

“These revelations demonstrate once again that the pledges to combat discrimination policing has undertaken through the race action plan are failing to be integrated into wider practice. Our reports have warned that innovative tools are being implemented in a context where ethnic inequalities, weak scrutiny and poor data collection already persist.

“Any use of facial recognition must meet rigorous official guidelines, be independently scrutinised, and prove it reduces rather than exacerbates ethnic bias.”

Official Statement

A Home Office spokesperson said: “The Home Office takes the conclusions of the report seriously and we have already taken action. A updated software has been externally evaluated and acquired, which has no statistically significant bias. It will be tested early next year and will be subject to evaluation.

“Our priority is ensuring public safety. This revolutionary tool will assist officers to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no further action would be pursued without specialist personnel carefully reviewing the results.”