🔗 Share this article

Law enforcement agencies across the United Kingdom successfully lobbied to use a face scanning system acknowledged as biased against females, young people, and members of ethnic minority groups, following complaints that a more accurate version generated a reduced number of potential suspects.

How the System Works

UK forces utilize the police national database (PND) to conduct retrospective facial recognition searches. This process involves matching a reference photograph of a person of interest against a database of over 19 million custody photos to identify possible hits.

Admitted Bias

The Home Office conceded last week that the technology was flawed. This admission came after a study by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and women at significantly higher rates than white men. The ministry said it “had acted on the findings”.

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

Known Issue

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

Senior officers were informed of the system's bias in September 2024. The government-ordered NPL review concluded the system was more likely to suggest incorrect matches for photos of women, 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 possible hits be increased to a level where the disparity was greatly diminished.

However, this decision was overturned the next month after forces complained that the adjusted system was producing a lower number of “investigative leads”. Internal records show the higher threshold cut the proportion of queries resulting in potential matches from 56% to a just 14%.

Severe Disparities

Although the authorities declined to specify what threshold is currently used, the recent independent review found the system could generate false positives for women of Black heritage almost 100 times more frequently than for Caucasian women at specific configurations.

The ministry stated on these results: “The testing identified that in a specific scenarios the software is more likely to wrongly flag some population segments in its match reports.”

Balancing Utility and Fairness

Outlining the impact of the temporary raise to the system's accuracy setting, the police records 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 add that forces complained that “a previously useful tool returned results of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has launched a two-and-a-half-month public review on its proposals to widen the use of facial recognition technology. The minister for police the relevant minister has labeled the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the police race action plan, said: “We observed very little consideration in race action plan meetings of the technology deployment despite obvious cross-over with the strategy's goals.

“This disclosure demonstrate once again that the pledges to combat discrimination the police has made via the equality initiative are not being translated into wider practice. Independent assessments have warned that innovative tools are being rolled out in a context where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

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

Official Statement

A Home Office spokesperson said: “The Home Office treat the findings of the study 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.

“The foremost aim is protecting the public. This revolutionary tool will assist police to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no arrest or charge would be pursued without specialist personnel meticulously examining the output.”