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Law enforcement agencies across the United Kingdom successfully lobbied to deploy a face scanning system acknowledged as biased against women, youths, and members of ethnic minority groups, after complaining that a less biased version produced a reduced number of potential suspects.

The Technology in Practice

UK forces utilize the police national database (PND) to conduct searches using historical face recognition. This process involves comparing a “probe image” of a suspect against a repository of more than 19 million mugshots to identify possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the technology was biased. This admission followed a review by the government's National Physical Laboratory found it incorrectly matched Black and Asian people and women at significantly higher rates than white men. The Home Office said it “took steps on the findings”.

“It prompts the issue of whether facial recognition only becomes useful if users accept discrimination in race and gender. Convenience is a poor argument for disregarding basic freedoms.”

Known Issue

Internal documents reveal that this bias has been recognized for more than a year. Furthermore, law enforcement argued to overturn an earlier ruling that was intended to mitigate the problem.

Police bosses were notified of the system's bias in late 2024. The government-ordered NPL review concluded the system was more likely to suggest false positives for photos of women, Black people, 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 possible hits be increased to a level where the disparity was significantly reduced.

However, this decision was reversed the next month after forces complained that the modified technology was producing fewer “investigative leads”. NPCC documents indicate the higher threshold cut the proportion of searches that yielded potential matches from 56% to a mere 14%.

Profound Inequalities

Although the authorities refused to say what threshold is currently used, the recent NPL study discovered the system could generate false positives for women of Black heritage nearly a hundred times more often than for white women at certain settings.

The Home Office commented on these findings: “Our evaluation found that in a limited set of circumstances the algorithm is has a greater tendency to incorrectly include some population segments in its match reports.”

Balancing Utility and Fairness

Outlining the impact of the temporary raise to the system's confidence threshold, the police records state: “The change significantly reduces the effect of bias across protected characteristics of race, generation and gender but had a substantially detrimental effect on operational effectiveness”. The papers further note that forces argued that “a once effective tactic now delivered results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a two-and-a-half-month public review on its plans to widen the use of biometric scanning systems. Policing minister Sarah Jones has described the tool as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the advisory panel for the police race action plan, commented: “There was scant discussion in equality strategy sessions of the technology deployment despite clear relevance with the plan’s concerns.

“These revelations demonstrate once again that the pledges to combat discrimination the police has made via the race action plan are failing to be integrated into broader operations. Independent assessments have cautioned that new technologies are being rolled out in a landscape where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

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

Home Office Response

A government representative stated: “We takes the conclusions of the study seriously and we have already taken action. A updated software has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be tested early next year and will be undergo further assessment.

“The foremost aim is protecting the public. This revolutionary tool will support officers to put criminals and rapists behind bars. There is human involvement in each stage of the process and no arrest or charge would be pursued without specialist personnel meticulously examining the results.”