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Police forces across the United Kingdom effectively campaigned to use a facial recognition system acknowledged as biased against women, youths, and members of minority ethnic backgrounds, after complaining that a less biased version generated fewer potential suspects.

How the System Works

UK forces use the national police database to carry out searches using historical face recognition. This procedure involves matching a reference photograph of a person of interest against a database of over 19 million custody photos to identify potential matches.

Acknowledged Discrimination

The Home Office conceded last week that the technology was flawed. This admission followed a study by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and females at significantly higher rates than Caucasian males. The ministry said it “had acted on the findings”.

“It prompts the question of whether this technology only becomes effective if users accept biases in race and sex. Convenience is a weak argument for overriding basic freedoms.”

Known Issue

Official papers show that this bias has been known about for more than a year. Furthermore, police forces lobbied to reverse an earlier ruling that was designed to address the problem.

Senior officers were notified of the system's bias in September 2024. The Home Office-commissioned NPL review found the system was had a higher probability to produce incorrect matches for images depicting women, Black people, and those under 40 years old.

A Policy U-Turn

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

However, this directive was overturned the next month following complaints from police that the modified technology was producing fewer “useful lines of inquiry”. NPCC documents show the higher threshold reduced the proportion of queries that yielded potential matches from over half to a just under 15%.

Profound Inequalities

Although the authorities refused to say what threshold is currently used, the recent NPL study discovered the system could generate false positives for Black women nearly a hundred times more frequently than for white women at certain settings.

The Home Office commented on these findings: “Our evaluation identified that in a limited set of circumstances the algorithm is has a greater tendency to wrongly flag 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 protected characteristics of ethnicity, generation and sex but had a significant negative impact on operational effectiveness”. The papers further note that forces complained that “a once effective tactic now delivered outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the UK administration has launched a two-and-a-half-month public review on its plans to expand the use of facial recognition technology. Policing minister the relevant minister has described the technology as the “most significant advance since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the advisory panel for the police race action plan, commented: “There was very little discussion in equality strategy sessions of the technology deployment even with clear relevance with the plan’s concerns.

“These revelations demonstrate yet again that the pledges to combat discrimination policing has made via the equality initiative are not being translated into wider practice. Independent assessments have cautioned that innovative tools are being rolled out in a landscape where racial disparities, inadequate oversight and faulty information gathering continue to exist.

“All deployment of this technology must meet rigorous official guidelines, be subject to external review, and prove it diminishes rather than compounds racial disparity.”

Home Office Response

A Home Office spokesperson stated: “The Home Office takes the findings of the study seriously and we have already taken action. A new algorithm has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be tested early next year and will be undergo further assessment.

“Our priority is protecting the public. This revolutionary tool will support officers to put criminals and rapists behind bars. There is officer review in each stage of the procedure and no further action would be taken without trained officers carefully reviewing the results.”