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Police forces across the UK successfully lobbied to deploy a face scanning system acknowledged as discriminatory against women, young people, and members of ethnic minority groups, following complaints that a more accurate version generated a reduced number of potential suspects.

How the System Works

UK forces utilize the police national database (PND) to carry out retrospective facial recognition searches. This process entails matching a reference photograph of a person of interest against a database of over 19 million custody photos to find potential matches.

Admitted Bias

The UK interior ministry admitted last week that the technology was biased. This acknowledgment followed a study by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and women at significantly higher rates than Caucasian males. The Home Office said it “took steps on the findings”.

“This raises the question of whether this technology only becomes effective if users accept biases in race and sex. Convenience is a poor argument for disregarding basic freedoms.”

Long-Standing Problem

Official papers show that this bias has been recognized for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was designed to address the problem.

Police bosses were notified of the system's bias in late 2024. The Home Office-commissioned NPL review concluded the system was had a higher probability to suggest incorrect matches for photos of females, Black people, and those under 40 years old.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches be raised to a level where the bias was greatly diminished.

However, this directive was overturned the following month after forces complained that the adjusted system was generating a lower number of “useful lines of inquiry”. NPCC documents show the stricter setting cut the proportion of queries that yielded potential matches from over half to a just under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is now in operation, the latest independent review found the system could produce false positives for Black women almost 100 times more frequently than for Caucasian women at specific configurations.

The Home Office stated on these results: “Our evaluation found that in a specific scenarios the software is has a greater tendency to incorrectly include some population segments in its search results.”

Operational Effectiveness vs. Bias

Outlining the impact of the temporary raise to the system's accuracy setting, the NPCC documents state: “This adjustment greatly lessens the impact of discrimination across legally safeguarded attributes of ethnicity, age and gender but had a significant negative impact on police efficiency”. The papers add that forces complained that “a previously useful tool returned results of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has launched a two-and-a-half-month public review on its proposals to expand the use of biometric scanning systems. The minister for police the relevant minister has labeled the technology as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the police race action plan, commented: “We observed scant discussion through equality strategy sessions of the technology deployment despite obvious cross-over with the plan’s concerns.

“These revelations show once again that the pledges to combat discrimination policing has undertaken through the equality initiative are not being translated into wider practice. Independent assessments have warned that new technologies are being rolled out in a context where racial disparities, weak scrutiny and faulty information gathering already persist.

“Any use of facial recognition must meet strict national standards, be independently scrutinised, and prove it reduces rather than exacerbates ethnic bias.”

Home Office Response

A Home Office spokesperson said: “We takes the conclusions of the report with utmost gravity and we have implemented changes. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be trialled early next year and will be undergo further assessment.

“The foremost aim is protecting the public. This gamechanging technology will support officers to apprehend and prosecute offenders. There is human involvement in every step of the process and no further action would be pursued without specialist personnel carefully reviewing the results.”