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Police forces across the United Kingdom successfully lobbied to use a face scanning system acknowledged as biased against females, 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 use the police national database (PND) to carry out searches using historical face recognition. This procedure involves comparing a reference photograph of a person of interest against a repository of more than 19 million custody photos to identify potential matches.

Admitted Bias

The Home Office conceded last week that the system was flawed. This admission came after a review by the government's National Physical Laboratory determined it incorrectly matched people of Black and Asian heritage and women at much greater frequency than Caucasian males. The ministry stated it “took steps on the findings”.

“It prompts the issue of whether facial recognition only becomes effective if users tolerate biases in race and sex. Operational ease is a poor argument for disregarding fundamental rights.”

Long-Standing Problem

Official papers show that this discriminatory flaw has been recognized for over twelve months. Furthermore, law enforcement lobbied to reverse an earlier ruling that was intended to mitigate the problem.

Police bosses were informed of the system's bias in September 2024. The government-ordered NPL review found the system was had a higher probability to produce false positives for images depicting females, Black people, and those under 40 years old.

A Policy U-Turn

In response, the National Police Chiefs’ Council (NPCC) 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 following month after forces complained that the modified technology was generating fewer “useful lines of inquiry”. Internal records show the higher threshold reduced the proportion of queries resulting in potential matches from over half to a just 14%.

Profound Inequalities

Although the authorities refused to say what threshold is currently used, the latest independent review discovered the system could generate incorrect matches for women of Black heritage almost 100 times more frequently than for Caucasian women at specific configurations.

The Home Office stated on these findings: “The testing found that in a specific scenarios the algorithm is more likely to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Outlining the effect of the temporary raise to the system's confidence threshold, the police records note: “This adjustment significantly reduces the impact of discrimination across protected characteristics of race, generation and gender but had a substantially detrimental effect on police efficiency”. The papers add that forces complained that “a previously useful tool returned results of questionable value”.

Broader Rollout Plans

Meanwhile, the government has launched a two-and-a-half-month public review on its proposals to expand the use of biometric scanning systems. Policing minister Sarah Jones has labeled 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, commented: “We observed scant consideration in race action plan meetings of the technology deployment despite obvious cross-over with the strategy's goals.

“This disclosure demonstrate yet again that the pledges to combat discrimination the police has made 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 context where racial disparities, weak scrutiny and poor data collection continue to exist.

“All deployment of facial recognition must meet rigorous official guidelines, be independently scrutinised, and prove it diminishes rather than compounds racial disparity.”

Official Statement

A government representative stated: “We treat the conclusions of the study with utmost gravity and we have already taken action. A new algorithm has been externally evaluated and procured, which has demonstrated no measurable discrimination. It will be tested early next year and will be subject to further assessment.

“The foremost aim is protecting the public. This gamechanging technology will support police to apprehend and prosecute offenders. There is officer review in each stage of the process and no arrest or charge would be pursued without specialist personnel meticulously examining the output.”