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Police forces across the United Kingdom successfully lobbied to deploy a face scanning system acknowledged as biased against women, young people, and members of ethnic minority groups, following complaints that a more accurate version generated fewer potential suspects.

How the System Works

British police use the national police database to conduct searches using historical face recognition. This procedure involves comparing a “probe image” of a person of interest against a database of more than 19 million custody photos to find potential matches.

Admitted Bias

The UK interior ministry conceded last week that the technology was flawed. This admission came after a review by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and women at significantly higher rates than Caucasian males. The ministry stated it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes effective if users tolerate discrimination in race and gender. Operational ease is a poor argument for disregarding fundamental rights.”

Long-Standing Problem

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

Senior officers were informed of the system's bias in late 2024. The government-ordered NPL review concluded the system was more likely to suggest incorrect matches for images depicting females, Black people, and those aged 40 and under.

A Reversed Decision

In reaction, the national police leadership body mandated that the confidence threshold required for potential matches be raised to a point where the disparity was greatly diminished.

However, this decision was overturned the following month following complaints from police that the modified technology was producing a lower number of “investigative leads”. Internal records show the higher threshold reduced the proportion of queries that yielded potential matches from 56% to a just under 15%.

Severe Disparities

Although the authorities refused to say what threshold is currently used, the recent independent review found the system could generate incorrect matches for Black women nearly a hundred times more frequently than for white women at specific configurations.

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

Balancing Utility and Fairness

Outlining the effect of the brief increase to the system's accuracy setting, the police records state: “This adjustment greatly lessens the impact of discrimination across legally safeguarded attributes of ethnicity, generation and sex but had a significant negative impact on police efficiency”. The papers add that forces argued that “a once effective tactic now delivered outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a ten-week public review on its plans to expand the use of biometric scanning systems. The minister for police Sarah Jones has described the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the national policing equality strategy, said: “There was very little consideration through race action plan meetings of the technology deployment even with clear relevance with the plan’s concerns.

“This disclosure demonstrate yet again that the pledges to combat discrimination the police has made through the equality initiative are failing to be integrated into broader operations. Our reports have warned that innovative tools are being rolled out in a context where ethnic inequalities, weak scrutiny and faulty information gathering already persist.

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

Home Office Response

A Home Office spokesperson said: “We takes the conclusions of the study with utmost gravity and we have already taken action. A new algorithm has been externally evaluated and acquired, which has no statistically significant bias. It will be tested in the coming months and will be undergo evaluation.

“The foremost aim is ensuring public safety. This gamechanging technology will assist officers to apprehend and prosecute offenders. There is human involvement in each stage of the process and no arrest or charge would be taken without specialist personnel carefully reviewing the results.”