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Police forces across the UK effectively campaigned to deploy a face scanning system acknowledged as biased against women, young people, and members of minority ethnic backgrounds, after complaining 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 matching a reference photograph of a person of interest against a database of more than 19 million custody photos to identify possible hits.

Admitted Bias

The Home Office conceded last week that the system was flawed. This acknowledgment followed a review by the National Physical Laboratory (NPL) found it incorrectly matched people of Black and Asian heritage and females at much greater frequency than Caucasian males. The Home Office said it “took steps on the findings”.

“It prompts the question of whether facial recognition only becomes useful if users accept biases in race and gender. Operational ease is a weak argument for overriding basic freedoms.”

Known Issue

Internal documents reveal that this discriminatory flaw has been recognized for more than a year. Furthermore, law enforcement lobbied to reverse an earlier ruling that was designed to mitigate the problem.

Senior officers were notified of the system's bias in late 2024. The government-ordered laboratory study concluded the system was had a higher probability to produce false positives for images depicting females, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches 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 modified technology was generating fewer “useful lines of inquiry”. Internal records show the higher threshold cut the number of queries resulting in potential matches from 56% to a just 14%.

Severe Disparities

Although the authorities refused to say what setting is currently used, the latest NPL study found the system could produce incorrect matches for women of Black heritage almost 100 times more frequently than for Caucasian women at certain settings.

The ministry commented on these results: “The testing identified that in a specific scenarios the algorithm is has a greater tendency to incorrectly include some demographic groups in its match reports.”

Balancing Utility and Fairness

Outlining the effect of the brief increase to the system's confidence threshold, the NPCC documents note: “This adjustment significantly reduces the effect of discrimination across protected characteristics of race, generation and sex but had a substantially detrimental effect on operational effectiveness”. The documents add that police units complained that “a once effective tactic returned outcomes 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 described the tool as the “most significant advance since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the independent scrutiny and oversight board for the police race action plan, said: “We observed very little consideration through race action plan meetings of the technology deployment despite clear relevance with the plan’s concerns.

“These revelations show yet again that the pledges to combat discrimination policing has undertaken via the race action plan are failing to be integrated into broader operations. Independent assessments have cautioned that new technologies are being rolled out in a landscape where racial disparities, weak scrutiny and faulty information gathering already persist.

“All deployment of this technology must adhere to strict national standards, be independently scrutinised, and demonstrate it reduces rather than exacerbates ethnic bias.”

Official Statement

A Home Office spokesperson said: “We takes the findings of the study seriously and we have implemented changes. 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 support police to put criminals and rapists behind bars. There is human involvement in each stage of the process and no further action would be pursued without trained officers meticulously examining the results.”