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Law enforcement agencies across the UK effectively campaigned to deploy a face scanning system known to be discriminatory against women, young people, and individuals from minority ethnic backgrounds, after complaining that a less biased version generated fewer potential suspects.

How the System Works

British police utilize the police national database (PND) to carry out retrospective facial recognition searches. This procedure entails matching a reference photograph of a suspect against a database of more than 19 million custody photos to find possible hits.

Admitted Bias

The UK interior ministry admitted last week that the system was flawed. This admission came after a review by the National Physical Laboratory (NPL) determined it misidentified people of Black and Asian heritage and women at much greater frequency than Caucasian males. The ministry stated it “took steps on the findings”.

“It prompts the question of whether this technology only becomes useful if users accept discrimination in race and gender. Convenience is a poor argument for disregarding fundamental rights.”

Known Issue

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

Senior officers were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned NPL review found the system was more likely to suggest false positives for images depicting females, Black people, and those aged 40 and under.

A Policy U-Turn

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 directive was overturned the following month following complaints from police that the adjusted system was producing a lower number of “useful lines of inquiry”. NPCC documents show the stricter setting reduced the number of searches that yielded potential matches from over half to a mere under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is now in operation, the recent NPL study found the system could generate false positives for Black women nearly a hundred times more often than for Caucasian women at certain settings.

The ministry stated on these findings: “The testing identified 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

Describing the impact of the brief increase to the system's accuracy setting, the police records state: “The change significantly reduces the effect of bias across protected characteristics of ethnicity, age and sex but had a substantially detrimental effect on police efficiency”. The papers further note that forces complained that “a once effective tactic now delivered outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month public review on its proposals to expand the use of biometric scanning systems. Policing minister the relevant minister has described the tool as the “biggest breakthrough since genetic fingerprinting”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the advisory panel for the police race action plan, commented: “There was very little discussion through race action plan meetings of the facial recognition rollout despite obvious cross-over with the strategy's goals.

“This disclosure show yet again that the anti-racism commitments the police has undertaken through the equality initiative are failing to be integrated into wider practice. Our reports have cautioned that innovative tools are being implemented in a context where racial disparities, inadequate oversight and faulty information gathering continue to exist.

“Any use of this technology must adhere to rigorous official guidelines, be independently scrutinised, and prove it diminishes rather than compounds racial disparity.”

Home Office Response

A Home Office spokesperson stated: “We treat the findings of the study with utmost gravity and we have already taken action. A new algorithm has been externally evaluated and procured, 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 revolutionary tool will assist police to apprehend and prosecute offenders. There is officer review in each stage of the procedure and no arrest or charge would be taken without specialist personnel meticulously examining the output.”