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Police forces across the UK successfully lobbied to use a face scanning system acknowledged as discriminatory against females, young people, and individuals from ethnic minority groups, following complaints that a more accurate version generated a reduced number of potential suspects.

The Technology in Practice

British police utilize the police national database (PND) to conduct retrospective facial recognition searches. This procedure involves matching a “probe image” of a person of interest against a database of more than 19 million mugshots to identify potential matches.

Admitted Bias

The UK interior ministry conceded last week that the system was biased. This acknowledgment came after a study by the government's National Physical Laboratory determined it incorrectly matched people of Black and Asian heritage and women at significantly higher rates than white men. The Home Office stated it “took steps on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users accept discrimination in race and sex. Convenience is a poor argument for overriding basic freedoms.”

Long-Standing Problem

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

Police bosses were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study found the system was more likely to produce false positives for photos of women, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

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

However, this decision was reversed the next month after forces complained that the modified technology was producing fewer “investigative leads”. NPCC documents show the higher threshold reduced the proportion of queries resulting in possible identifications from over half to a just 14%.

Profound Inequalities

Although the authorities refused to say what threshold is now in operation, the recent independent review discovered the system could generate false positives for Black women almost 100 times more often than for Caucasian women at specific configurations.

The Home Office stated on these findings: “Our evaluation identified that in a specific scenarios the algorithm is more likely to incorrectly include some population segments 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: “This adjustment significantly reduces the effect of bias across legally safeguarded attributes of race, age and sex but had a significant negative impact on police efficiency”. The documents add that forces complained that “a previously useful tool now delivered outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week public review on its proposals to widen the use of biometric scanning systems. The minister for police Sarah Jones has labeled the technology as the “biggest breakthrough since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the national policing equality strategy, said: “We observed very little discussion through equality strategy sessions of the facial recognition rollout despite clear relevance with the strategy's goals.

“These revelations show once again that the pledges to combat discrimination the police has undertaken via the equality initiative are failing to be integrated into broader operations. Independent assessments have warned that new technologies are being rolled out in a landscape where ethnic inequalities, weak scrutiny and poor data collection continue to exist.

“Any use of this technology must adhere to strict national standards, be subject to external review, and prove it reduces rather than exacerbates ethnic bias.”

Home Office Response

A Home Office spokesperson said: “The Home Office takes the conclusions of the study seriously and we have implemented changes. A updated software has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be undergo further assessment.

“The foremost aim is ensuring public safety. This gamechanging technology will support officers to put criminals and rapists behind bars. There is human involvement in each stage of the process and no further action would be taken without trained officers meticulously examining the results.”