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Law enforcement agencies across the UK effectively campaigned to use a face scanning system acknowledged as biased against women, youths, and members of ethnic minority groups, after complaining that a more accurate version produced a reduced number of investigative leads.

How the System Works

UK forces utilize the national police database to conduct retrospective facial recognition searches. This procedure entails comparing a reference photograph of a person of interest against a database of over 19 million custody photos to find potential matches.

Acknowledged Discrimination

The Home Office admitted last week that the technology was flawed. This admission followed a review by the National Physical Laboratory (NPL) determined it incorrectly matched Black and Asian people and females at significantly higher rates than Caucasian males. The ministry said it “took steps on the findings”.

“This raises the question of whether facial recognition only becomes useful if users accept discrimination in ethnicity and gender. Convenience is a poor argument for overriding fundamental rights.”

Known Issue

Official papers reveal that this bias has been known about for more than a year. Furthermore, law enforcement lobbied to reverse an earlier ruling that was designed to mitigate the problem.

Police bosses were notified of the system's bias in September 2024. The government-ordered NPL review concluded the system was more likely to suggest incorrect matches for photos of women, Black people, and those under 40 years old.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches be increased to a point where the disparity was significantly reduced.

However, this decision was reversed the following month after forces complained that the adjusted system was generating fewer “investigative leads”. NPCC documents show the stricter setting reduced the proportion of searches resulting in possible identifications from over half to a just under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is now in operation, the latest independent review discovered the system could generate false positives for Black women almost 100 times more frequently than for white women at certain settings.

The Home Office stated on these results: “The testing found that in a limited set of circumstances the algorithm is more likely to incorrectly include some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents note: “The change significantly reduces the effect of bias across protected characteristics of ethnicity, age and gender but had a substantially detrimental effect on police efficiency”. The documents further note that forces complained that “a once effective tactic now delivered outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a two-and-a-half-month public review on its proposals to widen the use of facial recognition technology. Policing minister Sarah Jones has described the tool as the “most significant advance since genetic fingerprinting”.

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, commented: “There was very little consideration in race action plan meetings of the facial recognition rollout despite obvious cross-over with the plan’s concerns.

“These revelations demonstrate yet again that the pledges to combat discrimination policing has made via the equality initiative are failing to be integrated into wider practice. Our reports have warned that innovative tools are being implemented in a context where ethnic inequalities, inadequate oversight and poor data collection already persist.

“All deployment of this technology must meet rigorous official guidelines, be independently scrutinised, and prove it diminishes rather than compounds ethnic bias.”

Official Statement

A Home Office spokesperson said: “The Home Office treat the conclusions of the report seriously and we have already taken action. A updated software has been externally evaluated and procured, which has no statistically significant bias. It will be tested in the coming months and will be undergo evaluation.

“Our priority is protecting the public. This gamechanging technology will assist police to put criminals and rapists behind bars. There is officer review in every step of the procedure and no further action would be taken without specialist personnel meticulously examining the results.”