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Police forces across the UK effectively campaigned to use a facial recognition system known to be biased against females, youths, and individuals from ethnic minority groups, following complaints that a more accurate version generated fewer investigative leads.

The Technology in Practice

British police use the national police database to carry out searches using historical face recognition. This procedure involves matching a “probe image” of a person of interest against a repository of more than 19 million mugshots to identify possible hits.

Acknowledged Discrimination

The Home Office admitted last week that the technology was biased. This admission came after 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 said it “took steps on the findings”.

“This raises the question of whether facial recognition only becomes effective if users accept discrimination in race and sex. Operational ease is a weak argument for disregarding basic freedoms.”

Long-Standing Problem

Internal documents reveal that this discriminatory flaw has been known about for more than a year. Furthermore, police forces argued to overturn an initial decision that was intended to address the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned NPL review concluded the system was more likely to suggest false positives for images depicting women, Black people, and those under 40 years old.

A Policy U-Turn

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

However, this decision was reversed the following month following complaints from police that the adjusted system was producing a lower number of “investigative leads”. Internal records indicate the higher threshold reduced the number of searches that yielded potential matches from 56% to a just under 15%.

Profound Inequalities

Although the Home Office and NPCC declined to specify what threshold is currently used, the latest independent review found the system could produce incorrect matches for women of Black heritage almost 100 times more frequently than for Caucasian women at specific configurations.

The Home Office commented on these findings: “The testing found that in a specific scenarios the algorithm is has a greater tendency to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Outlining the effect of the temporary raise to the system's confidence threshold, the police records state: “The change greatly lessens the effect of discrimination across protected characteristics of race, generation and gender but had a substantially detrimental effect on police efficiency”. The papers add that forces argued that “a previously useful tool now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a ten-week consultation on its plans to widen the use of biometric scanning systems. Policing minister the relevant minister has described the tool as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

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

“These revelations show yet again that the pledges to combat discrimination policing has made via the race action plan are failing to be integrated into wider practice. Our reports have warned that innovative tools are being implemented in a landscape where ethnic inequalities, weak scrutiny and faulty information gathering continue to exist.

“Any use of facial recognition must meet rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than compounds ethnic bias.”

Home Office Response

A government representative stated: “The Home Office treat the findings of the report with utmost gravity and we have implemented changes. A new algorithm has been independently tested and procured, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be subject to further assessment.

“The foremost aim is ensuring public safety. This gamechanging technology will support police to put criminals and rapists behind bars. There is human involvement in every step of the process and no further action would be taken without specialist personnel meticulously examining the results.”