🔗 Share this article

Law enforcement agencies across the UK successfully lobbied to use a face scanning system known to be discriminatory against females, young people, and members of ethnic minority groups, after complaining that a less biased version generated fewer investigative leads.

The Technology in Practice

UK forces utilize the national police database to carry out searches using historical face recognition. This procedure entails matching a “probe image” of a person of interest against a repository of over 19 million custody photos to identify potential matches.

Admitted Bias

The Home Office admitted last week that the technology was flawed. This admission followed a review by the government's National Physical Laboratory found it misidentified people of Black and Asian heritage and women at significantly higher rates than Caucasian males. The Home Office said it “had acted on the findings”.

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

Long-Standing Problem

Internal documents reveal that this discriminatory flaw has been known about for more than a year. Furthermore, law enforcement lobbied to reverse an initial decision that was designed to address the problem.

Police bosses were notified of the system's bias in September 2024. The Home Office-commissioned laboratory study concluded the system was more likely to produce false positives for photos of women, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In response, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches be raised to a level where the bias was significantly reduced.

However, this directive was reversed the following month following complaints from police that the modified technology was producing a lower number of “investigative leads”. NPCC documents show the higher threshold cut the proportion of queries that yielded possible identifications from over half to a just 14%.

Profound Inequalities

Although the Home Office and NPCC declined to specify what threshold is now in operation, the recent independent review discovered the system could generate incorrect matches for women of Black heritage nearly a hundred times more often 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 incorrectly include some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Outlining the impact of the brief increase to the system's accuracy setting, the NPCC documents note: “The change significantly reduces the impact of bias across protected characteristics of race, age and gender but had a substantially detrimental effect on police efficiency”. The documents add that police units complained that “a once effective tactic returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week public review on its proposals to expand the use of biometric scanning systems. Policing minister Sarah Jones has described the technology as the “most significant advance since genetic fingerprinting”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the independent scrutiny and oversight board for the police race action plan, said: “There was scant discussion in equality strategy sessions of the facial recognition rollout despite clear relevance with the plan’s concerns.

“This disclosure show once again that the pledges to combat discrimination the police has undertaken via the race action plan are failing to be integrated into wider practice. Our reports have cautioned that new technologies are being rolled out in a landscape where racial disparities, inadequate oversight and faulty information gathering already persist.

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

Home Office Response

A Home Office spokesperson stated: “We takes the conclusions of the study with utmost gravity and we have already taken action. A new algorithm has been independently tested and procured, which has demonstrated no measurable discrimination. It will be tested early next year and will be undergo further assessment.

“Our priority is protecting the public. This revolutionary tool will support officers to apprehend and prosecute offenders. There is human involvement in every step of the procedure and no further action would be taken without trained officers carefully reviewing the output.”