🔗 Share this article

Police forces across the United Kingdom successfully lobbied to use a facial recognition system acknowledged as biased against females, young people, and members of minority ethnic backgrounds, following complaints that a less biased version generated a reduced number of potential suspects.

The Technology in Practice

UK forces use the national police database to conduct searches using historical face recognition. This procedure involves matching a reference photograph of a suspect against a repository of more than 19 million custody photos to identify potential matches.

Admitted Bias

The Home Office admitted last week that the technology was flawed. This acknowledgment came after a review by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and women at much greater frequency 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 biases in race and sex. Operational ease is a weak argument for overriding basic freedoms.”

Known Issue

Internal documents show that this bias has been recognized for over twelve months. Furthermore, police forces argued to overturn 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 laboratory study concluded the system was more likely to suggest false positives for images depicting females, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for possible hits be raised to a point where the bias was significantly reduced.

However, this directive was overturned the next month after forces complained that the modified technology was generating a lower number of “useful lines of inquiry”. NPCC documents show the stricter setting cut the number of searches that yielded possible identifications from over half to a just under 15%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold is now in operation, the recent NPL study found the system could generate false positives for Black women almost 100 times more often than for Caucasian women at specific configurations.

The ministry stated on these findings: “The testing found that in a specific scenarios the algorithm is has a greater tendency to wrongly flag some population segments in its search results.”

Balancing Utility and Fairness

Outlining the impact of the temporary raise to the system's accuracy setting, the police records note: “The change greatly lessens the effect of bias across legally safeguarded attributes of race, age and gender but had a significant negative impact on operational effectiveness”. The papers add that police units argued that “a once effective tactic returned results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a ten-week consultation on its plans to expand the use of biometric scanning systems. The minister for police Sarah Jones has described the tool as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “There was scant consideration through race action plan meetings of the technology deployment even with clear relevance with the plan’s concerns.

“This disclosure show once again that the anti-racism commitments the police has made through the race action plan are failing to be integrated into broader operations. Independent assessments have warned that innovative tools are being rolled out in a landscape where racial disparities, inadequate oversight and poor data collection continue to exist.

“Any use of facial recognition must meet rigorous official guidelines, be independently scrutinised, and prove it reduces rather than exacerbates ethnic bias.”

Home Office Response

A government representative said: “We treat the conclusions of the report with utmost gravity and we have implemented changes. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be tested early next year and will be undergo evaluation.

“Our priority is protecting the public. This gamechanging technology will assist police to apprehend and prosecute offenders. There is officer review in every step of the process and no further action would be taken without trained officers meticulously examining the results.”