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Police forces across the UK effectively campaigned to deploy a facial recognition system known to be biased against women, young people, and members of minority ethnic backgrounds, following complaints that a more accurate version generated a reduced number of investigative leads.

How the System Works

British police utilize the police national database (PND) to carry out searches using historical face recognition. This process entails matching a reference photograph of a suspect against a repository of more than 19 million mugshots to find possible hits.

Acknowledged Discrimination

The UK interior ministry conceded last week that the system was biased. This admission came after a study by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and females at significantly higher rates than white men. The Home Office said it “had acted on the findings”.

“This raises the issue of whether this technology only becomes effective if users accept biases in race and sex. Operational ease is a weak argument for overriding fundamental rights.”

Known Issue

Internal documents show that this bias has been recognized for more than a year. Furthermore, police forces lobbied to reverse an initial decision that was designed to address the problem.

Senior officers were notified of the algorithmic discrimination in late 2024. The government-ordered laboratory study found the system was more likely to produce incorrect matches for photos of females, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

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

However, this decision was reversed the following month after forces complained that the modified technology was generating a lower number of “investigative leads”. NPCC documents indicate the higher threshold reduced the proportion of queries resulting in potential matches from over half to a just under 15%.

Profound Inequalities

Although the Home Office and NPCC declined to specify what threshold is now in operation, the latest NPL study found the system could produce incorrect matches for women of Black heritage almost 100 times more often than for Caucasian women at specific configurations.

The Home Office commented on these findings: “The testing identified that in a limited set of circumstances the algorithm is has a greater tendency to wrongly flag some population segments in its match reports.”

Balancing Utility and Fairness

Outlining the effect of the temporary raise to the system's confidence threshold, the police records state: “The change significantly reduces the effect of discrimination across protected characteristics of ethnicity, age and gender but had a significant negative impact on operational effectiveness”. The papers further note that police units argued that “a previously useful tool returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a two-and-a-half-month consultation on its proposals to widen the use of facial recognition technology. Policing minister the relevant minister has described the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the advisory panel for the police race action plan, commented: “We observed very little consideration in equality strategy sessions of the technology deployment despite clear relevance with the strategy's goals.

“This disclosure demonstrate yet again that the anti-racism commitments policing has undertaken via the race action plan are failing to be integrated into broader operations. Independent assessments have cautioned that innovative tools are being implemented in a context where racial disparities, inadequate oversight and faulty information gathering continue to exist.

“All deployment of this technology must adhere to rigorous official guidelines, be independently scrutinised, and prove it reduces rather than exacerbates ethnic bias.”

Official Statement

A government representative stated: “The Home Office treat the conclusions of the report with utmost gravity and we have already taken action. A new algorithm has been independently tested and procured, which has demonstrated no measurable discrimination. It will be trialled early next year and will be subject to evaluation.

“Our priority is protecting the public. This revolutionary tool will support police 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 carefully reviewing the results.”