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Police forces across the UK effectively campaigned to use a face scanning system known to be discriminatory against women, youths, and members of ethnic minority groups, after complaining that a less biased version generated fewer potential suspects.

The Technology in Practice

UK forces utilize the police national database (PND) to conduct searches using historical face recognition. This process entails comparing a reference photograph of a person of interest against a repository of over 19 million mugshots to identify potential matches.

Admitted Bias

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

“This raises the question of whether this technology only becomes useful if users accept biases in ethnicity and sex. Convenience is a poor argument for overriding fundamental rights.”

Known Issue

Official papers reveal that this bias has been known about for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was intended to mitigate the problem.

Police bosses were notified of the system's bias in late 2024. The government-ordered laboratory study found the system was more likely to suggest incorrect matches for photos of females, Black people, and those under 40 years old.

A Policy U-Turn

In reaction, the national police leadership body ordered that the confidence threshold required for possible hits be increased to a level where the disparity was greatly diminished.

However, this decision was overturned the next month following complaints from police that the modified technology was generating fewer “useful lines of inquiry”. NPCC documents indicate the stricter setting cut the proportion of queries that yielded possible identifications from over half to a mere under 15%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold is now in operation, the latest independent review found the system could produce incorrect matches for Black women almost 100 times more often than for white women at specific configurations.

The ministry commented on these findings: “The testing found that in a specific scenarios the algorithm is more likely to incorrectly include some demographic groups in its search results.”

Balancing Utility and Fairness

Outlining the impact of the brief increase to the system's accuracy setting, the NPCC documents note: “The change greatly lessens the effect of bias across legally safeguarded attributes of race, age and gender but had a significant negative impact on police efficiency”. The papers further note that police units argued that “a once effective tactic returned outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a ten-week consultation on its plans to expand the use of biometric scanning systems. The minister for police the relevant minister has labeled the technology as the “biggest breakthrough since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the independent scrutiny and oversight board for the police race action plan, commented: “There was scant discussion through equality strategy sessions of the technology deployment despite clear relevance with the strategy's goals.

“This disclosure show yet again that the pledges to combat discrimination the police has made through the race action plan are not being translated into wider practice. Independent assessments have warned that new technologies 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 rigorous official guidelines, be subject to external review, and prove it reduces rather than compounds ethnic bias.”

Official Statement

A government representative said: “The Home Office treat the findings of the study with utmost gravity and we have already taken action. A updated software has been externally evaluated and acquired, which has no statistically significant bias. It will be tested in the coming months and will be subject to further assessment.

“Our priority is ensuring public safety. This gamechanging technology will support police to put criminals and rapists behind bars. There is officer review in each stage of the process and no arrest or charge would be taken without specialist personnel carefully reviewing the output.”