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Law enforcement agencies across the United Kingdom successfully lobbied to use a facial recognition system acknowledged as biased against females, youths, and members of ethnic minority groups, following complaints that a less biased version generated a reduced number of investigative leads.

The Technology in Practice

UK forces use the police national database (PND) to conduct retrospective facial recognition searches. This process involves comparing a “probe image” of a person of interest against a repository of over 19 million mugshots to identify potential matches.

Admitted Bias

The Home Office conceded last week that the system was flawed. This admission came after a study by the government's National Physical Laboratory determined it incorrectly matched people of Black and Asian heritage and women at significantly higher rates than white men. The Home Office stated it “had acted on the findings”.

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

Known Issue

Internal documents reveal that this bias has been recognized for more than a year. Furthermore, law enforcement lobbied to reverse an initial decision that was designed to address the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The government-ordered NPL review concluded the system was had a higher probability to suggest incorrect matches for images depicting women, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In response, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for potential matches be raised to a point where the disparity was greatly diminished.

However, this directive was overturned the next month after forces complained that the adjusted system was producing a lower number of “investigative leads”. NPCC documents indicate the higher threshold cut the number of searches resulting in potential matches from 56% to a just 14%.

Profound Inequalities

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

The ministry commented on these results: “The testing identified that in a specific scenarios the algorithm is more likely to incorrectly include some demographic groups in its match reports.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's accuracy setting, the NPCC documents note: “This adjustment significantly reduces the impact of bias across legally safeguarded attributes of ethnicity, generation and sex but had a significant negative impact on police efficiency”. The documents further note that police units argued that “a previously useful tool now delivered outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has opened a two-and-a-half-month consultation on its proposals to expand the use of facial recognition technology. The minister for police the relevant minister has described the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, head of the independent scrutiny and oversight board for the police race action plan, commented: “There was scant discussion through equality strategy sessions of the facial recognition rollout even with clear relevance with the plan’s concerns.

“These revelations demonstrate yet again that the pledges to combat discrimination policing has made through the equality initiative are failing to be integrated into broader operations. Independent assessments have warned that innovative tools are being rolled out in a context where ethnic inequalities, inadequate oversight and faulty information gathering already persist.

“All deployment of facial recognition must meet rigorous official guidelines, be independently scrutinised, and prove it diminishes rather than exacerbates racial disparity.”

Home Office Response

A Home Office spokesperson stated: “The Home Office treat the findings of the study with utmost gravity and we have already taken action. A updated software has been independently tested and procured, 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 police to apprehend and prosecute offenders. There is human involvement in every step of the process and no arrest or charge would be pursued without trained officers carefully reviewing the output.”