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Law enforcement agencies across the UK successfully lobbied to deploy a face scanning system acknowledged as discriminatory against women, youths, and members of ethnic minority groups, following complaints that a more accurate version produced fewer investigative leads.

The Technology in Practice

UK forces use the national police database to conduct searches using historical face recognition. This procedure entails comparing a “probe image” of a suspect against a database of over 19 million custody photos to find possible hits.

Admitted Bias

The Home Office admitted last week that the system was flawed. This acknowledgment followed a review by the National Physical Laboratory (NPL) determined it incorrectly matched Black and Asian people and women at significantly higher rates than Caucasian males. The ministry stated it “took steps on the findings”.

“This raises the issue of whether this technology only becomes effective if users accept discrimination in race and sex. Operational ease is a weak argument for disregarding basic freedoms.”

Known Issue

Internal documents reveal that this discriminatory flaw has been known about for more than a year. Furthermore, law enforcement lobbied to reverse an earlier ruling that was intended to address the problem.

Police bosses were notified of the system's bias in September 2024. The Home Office-commissioned NPL review concluded 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 reaction, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for potential matches be increased to a level where the bias was greatly diminished.

However, this decision was overturned the next month after forces complained that the modified technology was generating fewer “useful lines of inquiry”. NPCC documents indicate the higher threshold reduced the proportion of searches that yielded possible identifications from over half to a mere 14%.

Severe Disparities

Although the authorities declined to specify what threshold is currently used, the recent NPL study found the system could produce incorrect matches for Black women nearly a hundred times more often than for white women at certain settings.

The Home Office commented on these findings: “The testing identified that in a specific scenarios the algorithm is has a greater tendency to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the impact of the temporary raise to the system's accuracy setting, the police records state: “This adjustment greatly lessens the effect of bias across protected characteristics of ethnicity, age and sex but had a substantially detrimental effect on police efficiency”. The documents further note that police units argued that “a once effective tactic returned outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month consultation on its proposals to widen the use of facial recognition technology. The minister for police Sarah Jones has labeled the tool as the “most significant advance since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the independent scrutiny and oversight board for the police race action plan, commented: “We observed scant discussion in race action plan meetings of the facial recognition rollout despite clear relevance with the strategy's goals.

“This disclosure show once again that the pledges to combat discrimination policing has undertaken through the race action plan are failing to be integrated into broader operations. Independent assessments have cautioned that new technologies are being rolled out in a landscape where racial disparities, weak scrutiny and poor data collection continue to exist.

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

Home Office Response

A government representative stated: “The Home Office takes the conclusions of the study with utmost gravity and we have implemented changes. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be tested early next year and will be subject to evaluation.

“Our priority is protecting the public. This revolutionary tool will assist officers to put criminals and rapists behind bars. There is human involvement in each stage of the process and no arrest or charge would be pursued without specialist personnel carefully reviewing the results.”