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Police forces across the United Kingdom effectively campaigned to use a face scanning system acknowledged as biased against females, young people, and members of ethnic minority groups, following complaints that a less biased version generated fewer potential suspects.

How the System Works

British police use the national police database to conduct retrospective facial recognition searches. This process entails comparing a “probe image” of a person of interest against a repository of over 19 million custody photos to identify potential matches.

Admitted Bias

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

“It prompts the question of whether facial recognition only becomes useful if users accept biases in ethnicity and sex. Convenience is a weak argument for overriding fundamental rights.”

Known Issue

Official papers reveal that this bias has been recognized for over twelve months. Furthermore, law enforcement lobbied to reverse an initial decision that was designed to mitigate the problem.

Police bosses were informed of the system's bias in September 2024. The government-ordered laboratory study found the system was had a higher probability to produce incorrect matches for photos of females, Black people, and those under 40 years old.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for possible hits be raised to a level where the bias was greatly diminished.

However, this decision was overturned the next month following complaints from police that the modified technology was producing a lower number of “investigative leads”. NPCC documents indicate the stricter setting cut the number of queries that yielded potential matches from 56% to a mere 14%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is currently used, the recent independent review found the system could generate incorrect matches for women of Black heritage almost 100 times more often than for Caucasian women at specific configurations.

The ministry stated on these results: “The testing identified that in a limited set of circumstances the algorithm is more likely to incorrectly include some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents state: “This adjustment significantly reduces the effect of discrimination across legally safeguarded attributes of ethnicity, age and gender but had a substantially detrimental effect on operational effectiveness”. The papers further note that police units complained that “a once effective tactic returned results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week public review on its plans to expand the use of biometric scanning systems. The minister for police the relevant minister has labeled the technology as the “biggest breakthrough since genetic fingerprinting”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “There was very little discussion in equality strategy sessions of the facial recognition rollout despite clear relevance with the strategy's goals.

“This disclosure show once again that the pledges to combat discrimination the police has undertaken via the race action plan are failing to be integrated into wider practice. Independent assessments have warned that innovative tools are being implemented in a landscape where racial disparities, inadequate oversight and faulty information gathering continue to exist.

“All deployment of facial recognition must adhere to strict national standards, be independently scrutinised, and demonstrate it diminishes rather than compounds ethnic bias.”

Official Statement

A government representative stated: “The Home Office treat the findings of the report seriously and we have already taken action. A updated software has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be subject to evaluation.

“The foremost aim is ensuring public safety. This gamechanging technology will assist officers 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 results.”