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Police forces across the United Kingdom effectively campaigned to deploy a face scanning system known to be biased against women, young people, and members of minority ethnic backgrounds, after complaining that a less biased version generated a reduced number of potential suspects.

The Technology in Practice

UK forces utilize the national police database to carry out searches using historical face recognition. This process entails comparing a “probe image” of a person of interest against a database of more than 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office conceded last week that the system was biased. This admission came after a study by the National Physical Laboratory (NPL) determined it misidentified people of Black and Asian heritage and females at significantly higher rates than Caucasian males. The ministry stated it “had acted on the findings”.

“This raises the issue of whether this technology only becomes useful if users tolerate biases in ethnicity and gender. Operational ease is a poor argument for overriding basic freedoms.”

Long-Standing Problem

Internal documents reveal that this discriminatory flaw has been recognized for more than a year. Furthermore, police forces lobbied to reverse an initial decision that was intended to mitigate the problem.

Police bosses were notified of the system's bias in September 2024. The Home Office-commissioned NPL review concluded the system was more likely to produce incorrect matches for photos of females, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In response, the national police leadership body ordered that the confidence threshold required for potential matches be increased to a level where the disparity was greatly diminished.

However, this decision was overturned the following month after forces complained that the adjusted system was generating fewer “useful lines of inquiry”. Internal records indicate the stricter setting cut the number of searches resulting in possible identifications from 56% to a just 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is now in operation, the latest NPL study found the system could generate incorrect matches for Black women almost 100 times more often than for Caucasian women at certain settings.

The ministry commented on these results: “Our evaluation found that in a limited set of circumstances the software is has a greater tendency to wrongly flag some population segments in its search results.”

Operational Effectiveness vs. Bias

Describing the impact of the brief increase to the system's accuracy setting, the police records state: “This adjustment significantly reduces the effect of bias across protected characteristics of race, age and sex but had a significant negative impact on operational effectiveness”. The papers add that forces complained that “a once effective tactic returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a ten-week consultation on its proposals to widen the use of facial recognition technology. The minister for police Sarah Jones has labeled the technology as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, head of the independent scrutiny and oversight board for the national policing equality strategy, said: “We observed scant discussion through equality strategy sessions of the technology deployment despite clear relevance with the strategy's goals.

“This disclosure show yet again that the anti-racism commitments policing has undertaken through 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 ethnic inequalities, inadequate oversight and faulty information gathering already persist.

“Any use of this technology must meet strict national standards, be independently scrutinised, and prove it diminishes rather than compounds racial disparity.”

Official Statement

A Home Office spokesperson stated: “The Home Office treat the conclusions of the study seriously and we have implemented changes. A new algorithm has been externally evaluated and acquired, which has no statistically significant bias. It will be trialled in the coming months and will be undergo further assessment.

“The foremost aim is ensuring public safety. This revolutionary tool will support officers to apprehend and prosecute offenders. There is human involvement in every step of the process and no further action would be taken without specialist personnel carefully reviewing the results.”