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Law enforcement agencies across the UK effectively campaigned to deploy a face scanning system known to be biased against females, youths, and individuals from ethnic minority groups, following complaints that a less biased version generated a reduced number of potential suspects.

How the System Works

British police utilize the national police database to conduct retrospective facial recognition searches. This process involves comparing a reference photograph of a suspect against a repository of more than 19 million custody photos to find possible hits.

Admitted Bias

The Home Office conceded last week that the technology was flawed. This admission followed a review by the National Physical Laboratory (NPL) determined it incorrectly matched 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 facial recognition only becomes effective if users tolerate biases in race and gender. Operational ease is a weak argument for disregarding basic freedoms.”

Known Issue

Internal documents show that this bias has been recognized for more than a year. Furthermore, law enforcement argued to overturn an initial decision that was intended 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 suggest false positives for images depicting females, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

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

However, this decision was reversed the next month following complaints from police that the modified technology was generating a lower number of “investigative leads”. Internal records show the stricter setting cut the proportion of queries resulting in potential matches from 56% to a just under 15%.

Profound Inequalities

Although the authorities declined to specify what setting is now in operation, the recent NPL study found the system could generate incorrect matches for Black women almost 100 times more often than for Caucasian women at specific configurations.

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

Operational Effectiveness vs. Bias

Describing the effect of the brief increase to the system's accuracy setting, the NPCC documents note: “The change significantly reduces the effect of bias across protected characteristics of race, age and gender but had a significant negative impact on police efficiency”. The papers further note that forces argued that “a previously useful tool returned outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the government has launched a two-and-a-half-month consultation on its plans to widen the use of biometric scanning systems. The minister for police the relevant minister has labeled the tool as the “most significant advance since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the independent scrutiny and oversight board for the national policing equality strategy, said: “There was very little discussion in race action plan meetings of the facial recognition rollout even with obvious cross-over with the strategy's goals.

“This disclosure demonstrate once again that the pledges to combat discrimination 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, weak scrutiny and poor data collection continue to exist.

“Any use of this technology must adhere to strict national standards, be subject to external review, and prove it diminishes rather than exacerbates ethnic bias.”

Official Statement

A government representative said: “The Home Office takes the findings of the report with utmost gravity and we have implemented changes. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be trialled in the coming months and will be undergo further assessment.

“Our priority is ensuring public safety. This gamechanging technology will support officers to put criminals and rapists behind bars. There is human involvement in every step of the process and no arrest or charge would be pursued without specialist personnel carefully reviewing the output.”