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Police forces across the United Kingdom successfully lobbied to deploy a face scanning system known to be biased against women, young people, and individuals from ethnic minority groups, after complaining that a less biased version generated a reduced number of potential suspects.

The Technology in Practice

UK forces utilize the national police database to carry out searches using historical face recognition. This process involves matching a reference photograph of a suspect against a repository of more than 19 million custody photos to find potential matches.

Admitted Bias

The Home Office admitted last week that the technology was biased. This admission came after a study by the government's National Physical Laboratory determined it incorrectly matched Black and Asian people and women at significantly higher rates than white men. The ministry said it “had acted on the findings”.

“This raises the question of whether this technology only becomes useful if users accept biases in race and sex. Convenience is a poor argument for overriding fundamental rights.”

Known Issue

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

Police bosses were notified of the system's bias in late 2024. The Home Office-commissioned NPL review found the system was more likely to produce false positives for photos of women, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for possible hits be increased to a point where the bias was greatly diminished.

However, this decision was reversed the following month after forces complained that the adjusted system was generating fewer “investigative leads”. NPCC documents indicate the stricter setting cut the proportion of searches that yielded possible identifications from over half to a just 14%.

Severe Disparities

Although the authorities declined to specify what setting is currently used, the latest NPL study found the system could generate false positives for Black women almost 100 times more often than for white women at specific configurations.

The Home Office stated on these results: “The testing found that in a limited set of circumstances the software is has a greater tendency to incorrectly include some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Outlining the impact of the brief increase to the system's accuracy setting, the police records state: “The change significantly reduces the impact of bias across legally safeguarded attributes of ethnicity, generation and gender but had a significant negative impact on police efficiency”. The papers add that forces argued that “a once effective tactic returned results of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a two-and-a-half-month consultation on its proposals to expand the use of biometric scanning systems. Policing minister Sarah Jones has described the technology as the “most significant advance since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “We observed scant consideration in race action plan meetings of the technology deployment despite obvious cross-over with the strategy's goals.

“This disclosure demonstrate once again that the pledges to combat discrimination the police has undertaken through the race action plan are not being translated into wider practice. Independent assessments have cautioned that innovative tools are being implemented in a landscape where ethnic inequalities, weak scrutiny and poor data collection already persist.

“Any use of this technology must adhere to rigorous official guidelines, be subject to external review, and demonstrate it diminishes rather than compounds racial disparity.”

Official Statement

A Home Office spokesperson stated: “The Home Office takes the findings of the report with utmost gravity and we have already taken action. A new algorithm has been independently tested and acquired, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be subject to evaluation.

“The foremost aim is protecting the public. This gamechanging technology will support police to apprehend and prosecute offenders. There is officer review in every step of the procedure and no further action would be pursued without specialist personnel meticulously examining the output.”