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Police forces across the UK effectively campaigned to deploy a facial recognition system acknowledged as biased against women, youths, and individuals from ethnic minority groups, after complaining that a more accurate version generated fewer investigative leads.

How the System Works

British police use the police national database (PND) to carry out retrospective facial recognition searches. This process involves matching a “probe image” of a person of interest against a database of over 19 million custody photos to find potential matches.

Acknowledged Discrimination

The UK interior ministry conceded last week that the technology was flawed. This admission came after a study by the National Physical Laboratory (NPL) determined it incorrectly matched people of Black and Asian heritage and females at significantly higher rates than Caucasian males. The Home Office stated it “took steps on the findings”.

“This raises the issue of whether this technology only becomes useful if users accept discrimination in race and sex. Operational ease is a weak argument for overriding basic freedoms.”

Known Issue

Internal documents show that this discriminatory flaw has been known about for over twelve months. Furthermore, law enforcement argued to overturn an initial decision that was intended to mitigate the problem.

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

A Reversed Decision

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

However, this directive was overturned the following month after forces complained that the adjusted system was generating a lower number of “investigative leads”. Internal records indicate the higher threshold reduced the proportion of searches that yielded potential matches from over half to a mere 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is currently used, the recent NPL study found the system could generate incorrect matches for women of Black heritage almost 100 times more frequently than for Caucasian women at certain settings.

The ministry stated on these findings: “Our evaluation identified that in a specific scenarios the software is more likely to wrongly flag some population segments in its match reports.”

Operational Effectiveness vs. Bias

Describing the impact of the temporary raise to the system's accuracy setting, the NPCC documents state: “The change significantly reduces the effect of discrimination across legally safeguarded attributes of race, generation and gender but had a significant negative impact on operational effectiveness”. The papers further note that police units argued that “a once effective tactic returned results of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a two-and-a-half-month consultation on its plans to expand the use of facial recognition technology. Policing minister the relevant minister has described the technology as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the police race action plan, said: “There was scant consideration in race action plan meetings of the facial recognition rollout even with clear relevance with the strategy's goals.

“This disclosure show yet again that the pledges to combat discrimination the police has made via the equality initiative are not being translated into broader operations. Our reports have warned that new technologies are being rolled out in a context where racial disparities, inadequate oversight and poor data collection continue to exist.

“All deployment of this technology must adhere to strict national standards, be independently scrutinised, and prove it diminishes rather than compounds racial disparity.”

Home Office Response

A government representative stated: “The Home Office treat the findings of the study with utmost gravity and we have already taken action. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be tested early next year and will be undergo further assessment.

“The foremost aim is protecting the public. This gamechanging technology will assist police to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no further action would be pursued without specialist personnel meticulously examining the output.”