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Law enforcement agencies across the UK successfully lobbied to use a face scanning system known to be biased against females, youths, and members of ethnic minority groups, after complaining that a more accurate version generated a reduced number of investigative leads.

How the System Works

UK forces use the police national database (PND) to conduct retrospective facial recognition searches. This procedure involves matching a reference photograph of a suspect against a repository of over 19 million mugshots to find possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the system was flawed. This acknowledgment followed a review by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and females at much greater frequency than white men. The ministry said it “had acted on the findings”.

“It prompts the question of whether this technology only becomes useful if users tolerate discrimination in ethnicity and gender. Convenience is a poor argument for overriding basic freedoms.”

Known Issue

Internal documents reveal that this bias has been recognized for more than a year. Furthermore, law enforcement argued to overturn an initial decision that was designed to mitigate the problem.

Senior officers were informed of the system's bias in September 2024. The Home Office-commissioned laboratory study concluded the system was had a higher probability to produce false positives for images depicting females, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for possible hits be raised to a level where the bias was significantly reduced.

However, this decision was reversed the following month following complaints from police that the modified technology was producing fewer “useful lines of inquiry”. NPCC documents show the higher threshold cut the proportion of searches that yielded possible identifications from over half to a mere under 15%.

Severe Disparities

Although the authorities refused to say what threshold is currently used, the recent NPL study discovered the system could generate false positives for women of Black heritage nearly a hundred times more often than for white women at certain settings.

The ministry commented on these findings: “Our evaluation identified that in a specific scenarios the software is more likely to incorrectly include some population segments in its search results.”

Operational Effectiveness vs. Bias

Describing the effect of the brief increase to the system's accuracy setting, the NPCC documents note: “This adjustment significantly reduces the effect of discrimination across protected characteristics of race, age and sex but had a significant negative impact on police efficiency”. The documents further note that forces complained that “a once effective tactic returned outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a two-and-a-half-month consultation on its plans to expand the use of biometric scanning systems. Policing minister the relevant minister has described the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the advisory panel for the national policing equality strategy, said: “There was very little consideration in race action plan meetings of the technology deployment despite obvious cross-over with the plan’s concerns.

“These revelations demonstrate yet again that the pledges to combat discrimination policing has undertaken via the race action plan are failing to be integrated into broader operations. Our reports have cautioned that innovative tools are being rolled out in a landscape where racial disparities, weak scrutiny and poor data collection continue to exist.

“All deployment of this technology must meet strict national standards, be independently scrutinised, and prove it reduces rather than exacerbates racial disparity.”

Official Statement

A government representative stated: “We treat the conclusions of the report with utmost gravity and we have already taken action. A updated software has been independently tested and procured, which has no statistically significant bias. It will be trialled early next year and will be undergo evaluation.

“Our priority is protecting the public. This gamechanging technology will assist police to apprehend and prosecute offenders. There is human involvement in every step of the process and no arrest or charge would be taken without trained officers carefully reviewing the output.”