🔗 Share this article

Law enforcement agencies across the United Kingdom successfully lobbied to use a face scanning system known to be biased against women, youths, and individuals from ethnic minority groups, following complaints that a less biased version produced fewer potential suspects.

The Technology in Practice

UK forces use the police national database (PND) to carry out retrospective facial recognition searches. This procedure involves comparing a “probe image” of a person of interest against a repository of over 19 million custody photos to find possible hits.

Admitted Bias

The Home Office admitted last week that the system was biased. This acknowledgment came after a review by the National Physical Laboratory (NPL) determined 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”.

“It prompts the issue of whether facial recognition only becomes effective if users tolerate biases in ethnicity and sex. Operational ease is a poor argument for overriding fundamental rights.”

Known Issue

Official papers show that this bias has been recognized for over twelve months. Furthermore, law enforcement lobbied to reverse an initial decision that was designed to mitigate the problem.

Police bosses were informed of the algorithmic discrimination in late 2024. The government-ordered NPL review concluded the system was had a higher probability to suggest false positives for photos of females, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

In response, the national police leadership body ordered that the confidence threshold required for potential matches be increased to a point where the bias was greatly diminished.

However, this decision was overturned the following month following complaints from police that the adjusted system was generating fewer “investigative leads”. NPCC documents indicate the higher threshold cut the number of queries that yielded possible identifications from 56% to a just under 15%.

Severe Disparities

Although the authorities declined to specify what setting is currently used, the latest NPL study found the system could generate false positives for Black women nearly a hundred times more frequently than for white women at specific configurations.

The Home Office stated on these findings: “The testing identified that in a limited set of circumstances the algorithm is more likely to wrongly flag some population segments in its match reports.”

Balancing Utility and Fairness

Outlining the effect of the brief increase to the system's accuracy setting, the police records state: “The change significantly reduces the effect of bias across legally safeguarded attributes of race, generation and gender but had a substantially detrimental effect on operational effectiveness”. The papers add that police units argued that “a once effective tactic now delivered results of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has launched a two-and-a-half-month public review on its proposals to expand the use of facial recognition technology. The minister for police Sarah Jones has labeled the technology as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, head of the independent scrutiny and oversight board for the national policing equality strategy, commented: “We observed scant consideration in race action plan meetings of the technology deployment even with obvious cross-over with the plan’s concerns.

“These revelations demonstrate yet again that the pledges to combat discrimination the police has made via the equality initiative are failing to be integrated into wider practice. Independent assessments have warned that new technologies are being rolled out in a context where racial disparities, inadequate oversight and poor data collection already persist.

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

Official Statement

A Home Office spokesperson stated: “We treat the findings of the study seriously and we have already taken action. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be trialled early next year and will be undergo evaluation.

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