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Law enforcement agencies across the UK successfully lobbied to use a facial recognition system known to be biased against women, youths, and members of minority ethnic backgrounds, after complaining that a more accurate version generated fewer potential suspects.

How the System Works

British police utilize the national police database to conduct searches using historical face recognition. This process entails matching a reference photograph of a suspect against a repository of more than 19 million mugshots to identify potential matches.

Admitted Bias

The Home Office admitted last week that the system was flawed. This admission followed a review by the National Physical Laboratory (NPL) determined it misidentified people of Black and Asian heritage and females at significantly higher rates than white men. The Home Office said it “took steps on the findings”.

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

Known Issue

Internal documents reveal that this bias has been known about for over twelve months. Furthermore, police forces argued to overturn an initial decision that was intended to mitigate the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The government-ordered laboratory study found the system was more likely to suggest false positives for images depicting women, Black people, and those under 40 years old.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the accuracy setting required for potential matches be increased to a level where the bias was greatly diminished.

However, this decision was overturned the next month after forces complained that the adjusted system was generating a lower number of “investigative leads”. NPCC documents indicate the higher threshold cut the number of searches resulting in potential matches from over half to a mere under 15%.

Profound Inequalities

Although the authorities declined to specify what threshold is currently used, the latest independent review found the system could generate false positives for Black women almost 100 times more often than for white women at certain settings.

The ministry commented on these findings: “The testing found that in a limited set of circumstances the software is more likely to incorrectly include some population segments in its search results.”

Balancing Utility and Fairness

Describing the impact of the brief increase to the system's confidence threshold, the police records state: “The change greatly lessens the impact of discrimination across protected characteristics of ethnicity, age and gender but had a substantially detrimental effect on police efficiency”. The documents add that forces complained that “a once effective tactic now delivered outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a two-and-a-half-month public review on its plans to widen the use of biometric scanning systems. Policing minister the relevant minister has described the technology as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the police race action plan, commented: “We observed very little consideration in race action plan meetings of the facial recognition rollout despite obvious cross-over with the plan’s concerns.

“These revelations show yet again that the anti-racism commitments the police has undertaken via the equality initiative are not being translated into wider practice. Independent assessments have warned that innovative tools are being implemented in a context where racial disparities, inadequate oversight and faulty information gathering already persist.

“Any use of facial recognition must meet rigorous official guidelines, be independently scrutinised, and prove it reduces rather than exacerbates ethnic bias.”

Official Statement

A Home Office spokesperson stated: “We takes the findings of the report seriously and we have implemented changes. A updated software has been independently tested and procured, which has no statistically significant bias. It will be tested in the coming months and will be undergo further assessment.

“The foremost aim is ensuring public safety. This revolutionary tool will support police to apprehend and prosecute offenders. There is officer review in every step of the procedure and no further action would be taken without specialist personnel carefully reviewing the output.”