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Law enforcement agencies across the UK effectively campaigned to deploy a face scanning system known to be biased against women, young people, and members of ethnic minority groups, following complaints that a less biased version produced a reduced number of investigative leads.

The Technology in Practice

UK forces use the police national database (PND) to carry out searches using historical face recognition. This process entails comparing a reference photograph of a suspect against a repository of over 19 million custody photos to identify potential matches.

Admitted Bias

The Home Office admitted last week that the technology was biased. This acknowledgment came after a review by the National Physical Laboratory (NPL) found it incorrectly matched people of Black and Asian heritage and women at significantly higher rates than Caucasian males. The ministry said it “took steps on the findings”.

“It prompts the question of whether this technology only becomes effective if users tolerate biases in race and sex. Operational ease is a weak argument for disregarding fundamental rights.”

Long-Standing Problem

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

Police bosses were notified of the algorithmic discrimination in late 2024. The Home Office-commissioned NPL review found the system was had a higher probability to suggest false positives for images depicting women, Black people, and those under 40 years old.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for possible hits be increased to a level where the bias was significantly reduced.

However, this decision was reversed the following month following complaints from police that the modified technology was generating fewer “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%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold is currently used, the latest independent review discovered the system could generate false positives for women of Black heritage almost 100 times more often than for Caucasian women at specific configurations.

The ministry stated on these findings: “Our evaluation identified that in a specific scenarios the software is more likely to incorrectly include some population segments in its search results.”

Operational Effectiveness vs. Bias

Outlining the impact of the temporary raise to the system's accuracy setting, the NPCC documents note: “The change greatly lessens the impact of discrimination across protected characteristics of ethnicity, generation and sex but had a substantially detrimental effect on police efficiency”. The papers add that forces complained that “a previously useful tool now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a ten-week public review on its plans to expand the use of facial recognition technology. The minister for police the relevant minister has described the tool as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair 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 even with obvious cross-over with the plan’s concerns.

“These revelations show once again that the anti-racism commitments policing has undertaken 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 landscape where ethnic inequalities, weak scrutiny 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 diminishes rather than compounds ethnic bias.”

Home Office Response

A government representative stated: “The Home Office treat the conclusions of the report seriously and we have implemented changes. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be tested early next year and will be subject to evaluation.

“The foremost aim is protecting the public. This gamechanging technology will assist police to apprehend and prosecute offenders. There is human involvement in each stage of the procedure and no arrest or charge would be taken without trained officers meticulously examining the results.”