🔗 Share this article

Police forces across the United Kingdom successfully lobbied to deploy a face scanning system known to be 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

British police use the national police database to conduct retrospective facial recognition searches. This process entails comparing a reference photograph of a suspect against a database of more than 19 million mugshots to find potential matches.

Admitted Bias

The Home Office admitted last week that the system was flawed. This admission followed a study by the government's National Physical Laboratory found it incorrectly matched people of Black and Asian heritage and females at much greater frequency than white men. The ministry stated it “took steps on the findings”.

“This raises the question of whether this technology only becomes effective if users tolerate biases in ethnicity and gender. Operational ease is a weak argument for disregarding basic freedoms.”

Known Issue

Official papers show that this bias has been recognized for more than a year. Furthermore, police forces argued to overturn an initial decision that was intended to address the problem.

Senior officers were notified of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study concluded the system was had a higher probability to suggest false positives for images depicting females, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for potential matches be increased to a level where the bias was significantly reduced.

However, this directive was reversed the next month after forces complained that the adjusted system was producing a lower number of “investigative leads”. NPCC documents show the higher threshold reduced the number of queries that yielded potential matches from 56% to a mere 14%.

Severe Disparities

Although the authorities refused to say what setting is now in operation, the latest NPL study found the system could generate incorrect matches for Black women almost 100 times more frequently than for Caucasian women at certain settings.

The ministry commented on these results: “Our evaluation identified that in a specific scenarios the software is more likely 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 confidence threshold, the police records state: “The change greatly lessens the effect of bias across protected characteristics of race, age and sex but had a substantially detrimental effect on police efficiency”. The documents further note that forces complained that “a once effective tactic returned outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has launched a ten-week public review on its proposals to expand the use of facial recognition technology. The minister for police the relevant minister has labeled the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the independent scrutiny and oversight board for the national policing equality strategy, commented: “We observed scant discussion in race action plan meetings of the technology deployment even with clear relevance with the plan’s concerns.

“This disclosure demonstrate yet again that the pledges to combat discrimination the police has undertaken through the equality initiative are not being translated into wider practice. Our reports have warned that new technologies are being implemented in a landscape where ethnic inequalities, weak scrutiny and faulty information gathering already persist.

“All deployment of this technology must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it reduces rather than exacerbates ethnic bias.”

Official Statement

A government representative stated: “The Home Office treat the conclusions of the report seriously and we have implemented changes. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be trialled in the coming months and will be subject to further assessment.

“Our priority is ensuring public safety. This gamechanging technology will assist police to put criminals and rapists behind bars. There is officer review in every step of the procedure and no further action would be pursued without trained officers carefully reviewing the results.”