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Police forces across the UK effectively campaigned to use a face scanning system acknowledged as discriminatory against women, youths, and individuals from minority ethnic backgrounds, after complaining that a less biased version produced fewer potential suspects.

How the System Works

British police utilize the police national database (PND) to carry out retrospective facial recognition searches. This procedure entails comparing a “probe image” of a person of interest against a repository of more than 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office conceded last week that the system was biased. This acknowledgment came after a review by the government's National Physical Laboratory found it incorrectly matched people of Black and Asian heritage and females at significantly higher rates than white men. The ministry stated it “had acted on the findings”.

“This raises the issue of whether this technology only becomes effective if users accept discrimination in ethnicity and sex. Operational ease is a poor argument for disregarding basic freedoms.”

Long-Standing Problem

Official papers show that this bias has been known about for more than a year. Furthermore, law enforcement lobbied to reverse an earlier ruling that was designed to address the problem.

Senior officers were notified of the system's bias in September 2024. The Home Office-commissioned NPL review concluded the system was more likely to produce incorrect matches for photos of women, Black people, and those aged 40 and under.

A Reversed Decision

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

However, this directive was reversed the next month following complaints from police that the adjusted system was producing fewer “useful lines of inquiry”. Internal records indicate the higher threshold cut the proportion of queries that yielded potential matches from 56% to a mere 14%.

Severe Disparities

Although the authorities refused to say what setting is currently used, the latest independent review found the system could produce false positives for women of Black heritage almost 100 times more often than for Caucasian women at specific configurations.

The ministry commented on these results: “The testing found that in a limited set of circumstances the software is more likely to incorrectly include some population segments in its search results.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the police records note: “This adjustment greatly lessens the effect of bias across legally safeguarded attributes of race, age and sex but had a significant negative impact on operational effectiveness”. The documents further note that police units argued that “a once effective tactic now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a ten-week public review on its proposals to expand the use of biometric scanning systems. The minister for police Sarah Jones has described the tool as the “most significant advance since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the independent scrutiny and oversight board for the police race action plan, commented: “There was very little discussion through equality strategy sessions of the technology deployment even with obvious cross-over with the strategy's goals.

“This disclosure demonstrate once again that the pledges to combat discrimination the police has made through the race action plan are failing to be integrated into broader operations. Independent assessments have cautioned that new technologies are being implemented in a context where ethnic inequalities, weak scrutiny and poor data collection already persist.

“All deployment of facial recognition must meet strict national standards, be independently scrutinised, and demonstrate it reduces rather than exacerbates racial disparity.”

Home Office Response

A government representative stated: “The Home Office treat the findings of the study with utmost gravity and we have already taken action. A new algorithm has been externally evaluated and procured, which has demonstrated no measurable discrimination. It will be tested early next year and will be undergo evaluation.

“The foremost aim is ensuring public safety. This gamechanging technology will assist officers to apprehend and prosecute offenders. There is human involvement in each stage of the process and no further action would be pursued without specialist personnel meticulously examining the results.”