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Law enforcement agencies across the United Kingdom successfully lobbied to use a facial recognition system known to be biased against females, youths, and individuals from ethnic minority groups, following complaints that a less biased version generated fewer investigative leads.

How the System Works

British police use the national police database to conduct searches using historical face recognition. This procedure involves comparing a “probe image” of a suspect against a database of more than 19 million custody photos to identify potential matches.

Acknowledged Discrimination

The Home Office admitted last week that the technology was biased. This acknowledgment came after a study by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and women at much greater frequency than Caucasian males. The Home Office said it “had acted on the findings”.

“It prompts the issue of whether facial recognition only becomes useful if users tolerate biases in race and gender. Convenience is a poor argument for overriding fundamental rights.”

Known Issue

Internal documents show that this bias has been recognized for over twelve months. Furthermore, law enforcement lobbied to reverse an earlier ruling that was intended to address the problem.

Police bosses were notified of the algorithmic discrimination in September 2024. The government-ordered NPL review concluded the system was more likely to produce incorrect matches for images depicting females, Black people, and those aged 40 and under.

A Policy U-Turn

In response, the national police leadership body mandated that the confidence threshold required for potential matches be increased to a level where the disparity was significantly reduced.

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

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is currently used, the recent NPL study found the system could produce false positives for Black women almost 100 times more frequently than for white women at specific configurations.

The Home Office commented on these findings: “Our evaluation identified that in a specific scenarios the software is has a greater tendency to incorrectly include some population segments in its match reports.”

Balancing Utility and Fairness

Outlining the effect of the temporary raise to the system's confidence threshold, the NPCC documents state: “The change greatly lessens the effect of discrimination across protected characteristics of ethnicity, generation and sex but had a substantially detrimental effect on operational effectiveness”. The documents add that police units argued that “a once effective tactic returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a ten-week public review on its proposals to expand the use of facial recognition technology. Policing minister the relevant minister has described the technology as the “biggest breakthrough since genetic fingerprinting”.

Expert and Oversight Concerns

Abimbola Johnson, head of the advisory panel for the national policing equality strategy, commented: “We observed scant discussion in equality strategy sessions of the technology deployment despite obvious cross-over with the strategy's goals.

“These revelations demonstrate once again that the pledges to combat discrimination policing has undertaken via the race action plan are not being translated into wider practice. Our reports have cautioned that innovative tools are being rolled out in a context where racial disparities, weak scrutiny and faulty information gathering already persist.

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

Home Office Response

A Home Office spokesperson said: “The Home Office treat the conclusions of the report 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 trialled early next year and will be undergo further assessment.

“The foremost aim is ensuring public safety. This revolutionary tool will support officers to put criminals and rapists behind bars. There is human involvement in every step of the process and no further action would be taken without trained officers carefully reviewing the output.”