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Police forces across the UK successfully lobbied to deploy a face scanning system known to be biased against women, youths, and individuals from ethnic minority groups, after complaining that a less biased version produced a reduced number of potential suspects.

How the System Works

British police utilize the national police database to carry out retrospective facial recognition searches. This process entails matching a “probe image” of a suspect against a database of more than 19 million mugshots to identify potential matches.

Admitted Bias

The Home Office conceded last week that the technology was biased. This admission followed a review by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and women at significantly higher rates than white men. The ministry stated it “took steps on the findings”.

“It prompts the issue of whether this technology only becomes effective if users tolerate discrimination in race and sex. Convenience is a poor argument for overriding basic freedoms.”

Known Issue

Internal documents show that this discriminatory flaw has been known about for more than a year. Furthermore, law enforcement argued to overturn an earlier ruling that was intended to mitigate the problem.

Senior officers were informed of the system's bias in late 2024. The Home Office-commissioned laboratory study found the system was more likely to suggest false positives for images depicting women, Black people, and those under 40 years old.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for possible hits be raised to a point where the disparity was significantly reduced.

However, this decision was reversed the next month after forces complained that the adjusted system was producing a lower number of “useful lines of inquiry”. NPCC documents show the higher threshold cut the proportion of queries resulting in potential matches from 56% to a just 14%.

Profound Inequalities

Although the Home Office and NPCC refused to say what setting is now in operation, the recent NPL study found the system could generate false positives for women of Black heritage almost 100 times more often than for Caucasian women at certain settings.

The ministry commented on these findings: “Our evaluation identified that in a limited set of circumstances the algorithm is has a greater tendency to incorrectly include some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Outlining the impact of the brief increase to the system's confidence threshold, the NPCC documents note: “This adjustment greatly lessens the effect of bias across legally safeguarded attributes of ethnicity, generation and sex but had a substantially detrimental effect on police efficiency”. The papers further note that forces complained that “a once effective tactic returned outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a two-and-a-half-month consultation on its proposals to expand the use of facial recognition technology. Policing minister Sarah Jones has described the tool as the “biggest breakthrough since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the police race action plan, said: “We observed very little consideration through equality strategy sessions of the facial recognition rollout despite clear relevance with the plan’s concerns.

“This disclosure demonstrate yet again that the pledges to combat discrimination policing has made through the race action plan are not being translated into broader operations. Independent assessments have cautioned that innovative tools are being rolled out in a context where racial disparities, inadequate oversight and poor data collection continue to exist.

“Any use of facial recognition must meet strict national standards, be subject to external review, and demonstrate it reduces rather than compounds ethnic bias.”

Home Office Response

A Home Office spokesperson stated: “The Home Office takes the findings of the study seriously and we have implemented changes. A updated software has been independently tested and acquired, 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 revolutionary tool will assist police to put criminals and rapists behind bars. There is officer review in every step of the procedure and no arrest or charge would be pursued without specialist personnel carefully reviewing the output.”