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Law enforcement agencies across the United Kingdom successfully lobbied to deploy a face scanning system acknowledged as biased against women, young people, and members of minority ethnic backgrounds, following complaints that a more accurate version produced a reduced number of investigative leads.

How the System Works

British police utilize the police national database (PND) to conduct searches using historical face recognition. This procedure entails matching a “probe image” of a suspect against a repository of more than 19 million mugshots to identify potential matches.

Acknowledged Discrimination

The Home Office admitted last week that the technology was flawed. This acknowledgment came after a study by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and females at significantly higher rates than white men. The Home Office stated it “took steps on the findings”.

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

Known Issue

Official papers reveal that this bias has been known about for more than a year. Furthermore, law enforcement lobbied to reverse an initial decision that was designed to address the problem.

Police bosses were notified of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study found the system was more likely to produce incorrect matches for images depicting females, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

In response, the national police leadership body mandated that the accuracy setting required for potential matches be increased to a point where the bias was significantly reduced.

However, this decision was reversed the next month following complaints from police that the modified technology was producing fewer “useful lines of inquiry”. NPCC documents show the higher threshold cut the proportion of searches that yielded potential matches from 56% to a just under 15%.

Severe Disparities

Although the authorities declined to specify what threshold is now in operation, the recent independent review found the system could generate false positives for Black women almost 100 times more frequently than for white women at specific configurations.

The ministry commented on these findings: “Our evaluation identified that in a limited set of circumstances the algorithm is more likely to wrongly flag some population segments in its match reports.”

Operational Effectiveness vs. Bias

Describing the impact 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 ethnicity, generation and gender but had a significant negative impact on police efficiency”. The papers further note that forces argued that “a previously useful tool returned results of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a two-and-a-half-month consultation on its plans to expand the use of biometric scanning systems. Policing minister the relevant minister has labeled the tool as the “most significant advance 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, said: “We observed scant consideration through equality strategy sessions of the technology deployment even with obvious cross-over with the strategy's goals.

“These revelations show yet again that the pledges to combat discrimination the police has made via the equality initiative are failing to be integrated into wider practice. Independent assessments have cautioned that new technologies are being rolled out in a context where ethnic inequalities, inadequate oversight and poor data collection continue to exist.

“All deployment of facial recognition must meet strict national standards, be subject to external review, and prove it reduces rather than exacerbates ethnic bias.”

Home Office Response

A government representative stated: “The Home Office treat the findings of the study with utmost gravity and we have implemented changes. A new algorithm has been externally evaluated and acquired, which has no statistically significant bias. It will be tested early next year and will be undergo further assessment.

“The foremost aim is ensuring public safety. This revolutionary tool will assist police to apprehend and prosecute offenders. There is officer review in every step of the procedure and no further action would be taken without trained officers meticulously examining the output.”