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Police forces across the UK effectively campaigned to deploy a face scanning system known to be biased against females, youths, and individuals from ethnic minority groups, following complaints that a less biased version generated a reduced number of investigative leads.

How the System Works

UK forces utilize the national police database to conduct retrospective facial recognition searches. This process entails matching a “probe image” of a person of interest against a repository of more than 19 million mugshots to find potential matches.

Acknowledged Discrimination

The Home Office admitted last week that the system was biased. This admission came after a study by the National Physical Laboratory (NPL) found it incorrectly matched people of Black and Asian heritage and females at much greater frequency than white men. The Home Office stated it “took steps on the findings”.

“It prompts the question of whether facial recognition only becomes effective if users tolerate biases in race and sex. Operational ease is a weak argument for disregarding basic freedoms.”

Known Issue

Official papers reveal that this discriminatory flaw has been known about for over twelve months. Furthermore, police forces argued to overturn an initial decision that was intended to address the problem.

Senior officers were notified of the system's bias in September 2024. The government-ordered laboratory study found the system was more likely to suggest false positives 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 accuracy setting required for possible hits be increased to a level where the disparity was significantly reduced.

However, this directive was overturned the following month after forces complained that the adjusted system was producing fewer “investigative leads”. Internal records indicate the stricter setting reduced the proportion of queries resulting in potential matches from 56% to a just under 15%.

Severe Disparities

Although the authorities declined to specify what setting is now in operation, the latest independent review found the system could produce incorrect matches for women of Black heritage almost 100 times more often than for Caucasian women at certain settings.

The ministry stated on these results: “The testing found that in a specific scenarios the software 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 state: “The change significantly reduces the impact of bias across protected characteristics of ethnicity, generation and gender but had a substantially detrimental effect on police efficiency”. The papers further note that police units complained that “a once effective tactic returned results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a ten-week consultation on its plans to expand the use of biometric scanning systems. The minister for police the relevant minister has described the tool as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, head of the independent scrutiny and oversight board for the national policing equality strategy, said: “There was very little discussion through race action plan meetings of the facial recognition rollout despite obvious cross-over with the plan’s concerns.

“This disclosure show yet again that the pledges to combat discrimination the police has undertaken through the race action plan are failing to be integrated into wider practice. Independent assessments have warned that innovative tools are being implemented in a context where ethnic inequalities, weak scrutiny and poor data collection continue to exist.

“All deployment of this technology must adhere to strict national standards, be independently scrutinised, and prove it reduces rather than compounds ethnic bias.”

Official Statement

A Home Office spokesperson stated: “The Home Office treat the findings of the study seriously 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 in the coming months and will be subject to further assessment.

“Our priority is protecting the public. This revolutionary tool will assist police to apprehend and prosecute offenders. There is human involvement in every step of the process and no arrest or charge would be taken without trained officers carefully reviewing the output.”