🔗 Share this article

Police forces across the UK successfully lobbied to deploy a facial recognition system known to be discriminatory against women, youths, and members of ethnic minority groups, following complaints that a less biased version generated a reduced number of potential suspects.

How the System Works

UK forces use 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 more than 19 million mugshots to find possible hits.

Admitted Bias

The Home Office admitted last week that the system was biased. This acknowledgment came after a review by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and females at significantly higher rates than Caucasian males. The Home Office stated it “took steps on the findings”.

“This raises the question of whether this technology only becomes effective if users accept discrimination in ethnicity and sex. Convenience is a weak argument for overriding basic freedoms.”

Known Issue

Official papers reveal that this discriminatory flaw has been recognized for more than a year. Furthermore, police forces argued to overturn an initial decision that was intended to mitigate the problem.

Senior officers were informed of the algorithmic discrimination in late 2024. The government-ordered NPL review found the system was had a higher probability to suggest incorrect matches for photos of women, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

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

However, this directive was reversed the following month after forces complained that the adjusted system was generating fewer “investigative leads”. NPCC documents show the stricter setting cut the number of searches that yielded potential matches from over half to a just 14%.

Severe Disparities

Although the Home Office and NPCC declined to specify what setting is currently used, the recent NPL study found the system could produce false positives for women of Black heritage almost 100 times more frequently than for Caucasian women at certain settings.

The Home Office stated on these findings: “Our evaluation found 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 effect of the temporary raise to the system's confidence threshold, the police records state: “This adjustment significantly reduces the effect of discrimination across protected characteristics of ethnicity, age and sex but had a significant negative impact on police efficiency”. The documents further note that forces argued that “a once effective tactic returned outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month public review on its proposals to expand the use of biometric scanning systems. Policing minister Sarah Jones has described the technology as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the police race action plan, said: “There was very little discussion in race action plan meetings of the technology deployment even with obvious cross-over with the strategy's goals.

“These revelations demonstrate once again that the pledges to combat discrimination policing has undertaken via the race action plan are failing to be integrated into broader operations. Independent assessments have warned that new technologies are being implemented in a landscape where racial disparities, 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.”

Home Office Response

A government representative said: “The Home Office takes the conclusions of the report 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 tested in the coming months and will be subject to evaluation.

“The foremost aim is protecting the public. This gamechanging technology will assist police to apprehend and prosecute offenders. There is officer review in every step of the procedure and no further action would be pursued without trained officers meticulously examining the results.”