🔗 Share this article

Law enforcement agencies across the UK successfully lobbied to use a face scanning system known to be biased against women, youths, and individuals from minority ethnic backgrounds, after complaining that a less biased version produced fewer potential suspects.

The Technology in Practice

British police use the police national database (PND) to conduct searches using historical face recognition. This process entails matching a reference photograph of a person of interest against a repository of over 19 million mugshots to find potential matches.

Admitted Bias

The Home Office conceded last week that the system was flawed. This acknowledgment came after a review by the government's National Physical Laboratory determined it incorrectly matched Black and Asian people and females at significantly higher rates than Caucasian males. The ministry stated it “had acted on the findings”.

“This raises the question of whether this technology only becomes effective if users tolerate biases in race and sex. Operational ease is a poor argument for overriding basic freedoms.”

Long-Standing Problem

Internal documents reveal that this bias has been recognized for over twelve months. Furthermore, police forces lobbied to reverse an initial decision that was intended to address the problem.

Senior officers were informed of the system's bias in September 2024. The Home Office-commissioned NPL review found the system was more likely to suggest false positives for photos of women, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

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

However, this decision was overturned the next month after forces complained that the adjusted system was generating a lower number of “useful lines of inquiry”. Internal records indicate the stricter setting cut the number of queries that yielded possible identifications from over half to a just 14%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold is currently used, the recent independent review discovered the system could generate incorrect matches for women of Black heritage nearly a hundred times more frequently than for white women at specific configurations.

The ministry stated on these findings: “Our evaluation identified that in a limited set of circumstances the software is more likely to wrongly flag some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Describing the impact of the temporary raise to the system's confidence threshold, the police records state: “The change significantly reduces the effect of bias across legally safeguarded attributes of ethnicity, generation and gender but had a significant negative impact on police efficiency”. The documents further note that police units argued that “a once effective tactic returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week consultation on its plans to widen the use of biometric scanning systems. Policing minister the relevant minister has described the tool as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, head of the advisory panel for the national policing equality strategy, said: “We observed very little consideration in race action plan meetings of the facial recognition rollout despite obvious cross-over with the strategy's goals.

“This disclosure demonstrate once again that the anti-racism commitments the police has made via the race action plan are not being translated into broader operations. Our reports have cautioned that innovative tools are being rolled out in a context where ethnic inequalities, weak scrutiny and faulty information gathering continue to exist.

“Any use of this technology must meet rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than compounds ethnic bias.”

Official Statement

A government representative said: “The Home Office treat the findings of the study seriously and we have implemented changes. A new algorithm has been independently tested and acquired, which has demonstrated no measurable discrimination. It will be tested early next year and will be subject to evaluation.

“The foremost aim is protecting the public. This gamechanging technology will support police to put criminals and rapists behind bars. There is human involvement in each stage of the procedure and no arrest or charge would be taken without trained officers meticulously examining the output.”