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Police forces across the United Kingdom effectively campaigned to deploy a face scanning system acknowledged as biased against females, young people, and individuals from ethnic minority groups, after complaining that a less biased version produced fewer investigative leads.

How the System Works

UK forces utilize the police national database (PND) to conduct searches using historical face recognition. This procedure involves comparing a “probe image” of a person of interest against a repository of more than 19 million mugshots to find potential matches.

Admitted Bias

The UK interior ministry conceded last week that the technology was flawed. 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 Caucasian males. The ministry said it “had acted on the findings”.

“This raises the question of whether facial recognition only becomes useful if users accept biases in ethnicity and gender. Operational ease is a weak argument for overriding basic freedoms.”

Long-Standing Problem

Internal documents reveal that this bias has been recognized for over twelve months. Furthermore, police forces lobbied to reverse an initial decision that was designed to mitigate the problem.

Police bosses were notified of the algorithmic discrimination in September 2024. The Home Office-commissioned NPL review concluded the system was more likely to suggest incorrect matches for images depicting women, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

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

However, this directive was overturned the next month following complaints from police that the adjusted system was generating a lower number of “investigative leads”. NPCC documents indicate the stricter setting cut the number of searches resulting in possible identifications from 56% to a just under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what setting is now in operation, the latest NPL study found the system could produce false positives for women of Black heritage nearly a hundred times more frequently than for white women at specific configurations.

The ministry stated on these findings: “The testing identified that in a limited set of circumstances the algorithm is has a greater tendency to incorrectly include some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Outlining the impact of the brief increase to the system's confidence threshold, the police records note: “This adjustment greatly lessens the impact of bias across protected characteristics of race, generation and gender but had a significant negative impact on operational effectiveness”. The documents further note that forces argued that “a once effective tactic returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a two-and-a-half-month public review on its plans to widen the use of biometric scanning systems. The minister for police the relevant minister has labeled the tool as the “biggest breakthrough since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the independent scrutiny and oversight board for the national policing equality strategy, commented: “We observed scant consideration in equality strategy sessions of the technology deployment despite clear relevance with the plan’s concerns.

“This disclosure show once again that the anti-racism commitments 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 racial disparities, inadequate oversight and faulty information gathering already persist.

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

Home Office Response

A government representative said: “The Home Office takes the conclusions of the study with utmost gravity and we have already taken action. A updated software has been independently tested and procured, which has no statistically significant bias. It will be trialled in the coming months and will be undergo further assessment.

“Our priority is ensuring public safety. This gamechanging technology will support officers to apprehend and prosecute offenders. There is human involvement in every step of the process and no arrest or charge would be taken without trained officers carefully reviewing the results.”