🔗 Share this article

Law enforcement agencies across the UK effectively campaigned to use a face scanning system acknowledged as biased against females, young people, and individuals from ethnic minority groups, following complaints that a more accurate version generated fewer potential suspects.

How the System Works

British police utilize the police national database (PND) to carry out searches using historical face recognition. This process entails matching a “probe image” of a suspect against a repository of more than 19 million mugshots to find possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the technology was biased. This admission followed a review by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and females at significantly higher rates than Caucasian males. The Home Office stated it “took steps on the findings”.

“This raises the question of whether this technology only becomes effective if users tolerate biases in ethnicity and gender. Operational ease is a weak argument for disregarding fundamental rights.”

Known Issue

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

Police bosses were notified of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study found the system was had a higher probability to suggest false positives for images depicting women, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

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

However, this decision was overturned the next month following complaints from police that the modified technology was producing a lower number of “investigative leads”. Internal records show the higher threshold reduced the proportion of searches resulting in potential matches from 56% to a just 14%.

Severe Disparities

Although the Home Office and NPCC declined to specify what setting is currently used, the recent NPL study found the system could produce incorrect matches for women of Black heritage nearly a hundred times more frequently than for Caucasian women at specific configurations.

The Home Office stated on these results: “Our evaluation found that in a specific scenarios the algorithm is more likely to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the effect of the brief increase to the system's confidence threshold, the NPCC documents state: “The change greatly lessens the effect of bias across protected characteristics of ethnicity, generation and sex but had a significant negative impact on operational effectiveness”. The papers add that forces complained that “a once effective tactic now delivered outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a ten-week consultation on its proposals to widen the use of facial recognition technology. Policing minister Sarah Jones has labeled the technology as the “most significant advance since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the independent scrutiny and oversight board for the national policing equality strategy, said: “We observed very little discussion through race action plan meetings of the facial recognition rollout despite clear relevance with the strategy's goals.

“These revelations show yet again that the pledges to combat discrimination policing has made via the equality initiative are failing to be integrated into wider practice. Our reports have warned that new technologies are being implemented in a context where racial disparities, weak scrutiny and poor data collection already persist.

“Any use of this technology must meet strict national standards, be subject to external review, and demonstrate it reduces rather than compounds racial disparity.”

Official Statement

A government representative said: “We takes the conclusions of the study with utmost gravity and we have implemented changes. A updated software has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be subject to further assessment.

“Our priority is protecting the public. This gamechanging technology will assist police to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no arrest or charge would be taken without trained officers meticulously examining the output.”