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Police forces across the United Kingdom successfully lobbied to use a face scanning system acknowledged as biased against women, young people, and individuals from minority ethnic backgrounds, after complaining that a more accurate version generated fewer potential suspects.

The Technology in Practice

UK forces utilize the police national database (PND) to carry out retrospective facial recognition searches. This procedure entails matching a “probe image” of a person of interest against a database of over 19 million custody photos to find potential matches.

Admitted Bias

The UK interior ministry admitted last week that the technology was flawed. This admission followed a study by the government's National Physical Laboratory determined it incorrectly matched people of Black and Asian heritage and females at significantly higher rates than white men. The Home Office said it “took steps on the findings”.

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

Known Issue

Official papers reveal that this bias has been known about for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was designed to mitigate the problem.

Police bosses were notified of the algorithmic discrimination in September 2024. The government-ordered laboratory study concluded the system was had a higher probability to produce false positives for photos of women, Black people, and those aged 40 and under.

A Policy U-Turn

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

However, this directive was overturned the following month following complaints from police that the modified technology was producing a lower number of “investigative leads”. NPCC documents show the stricter setting cut the number of searches that yielded possible identifications from 56% to a just under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is currently used, the latest NPL study found the system could produce false positives for Black women nearly a hundred times more often than for white women at certain settings.

The ministry commented on these findings: “The testing found that in a limited set of circumstances the algorithm is has a greater tendency to incorrectly include some population segments in its match reports.”

Operational Effectiveness vs. Bias

Describing the effect of the brief increase to the system's accuracy setting, the NPCC documents state: “This adjustment greatly lessens the effect of bias across legally safeguarded attributes of ethnicity, age and sex but had a substantially detrimental effect on police efficiency”. The documents add that forces complained that “a previously useful tool now delivered results of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month public review on its plans to expand the use of facial recognition technology. Policing minister Sarah Jones has labeled the technology 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: “There was scant consideration through equality strategy sessions of the technology deployment despite obvious cross-over with the plan’s concerns.

“This disclosure show yet again that the anti-racism commitments the police has undertaken through the race action plan are not being translated into wider practice. Independent assessments have cautioned that innovative tools are being implemented in a landscape where ethnic inequalities, inadequate oversight and poor data collection already persist.

“All deployment of this technology must adhere to strict national standards, be independently scrutinised, and demonstrate it diminishes rather than exacerbates ethnic bias.”

Home Office Response

A Home Office spokesperson said: “The Home Office treat the findings of the study seriously and we have already taken action. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be trialled in the coming months and will be subject to evaluation.

“The foremost aim is ensuring public safety. This revolutionary tool will assist police to put criminals and rapists behind bars. There is officer review in every step of the process and no further action would be pursued without specialist personnel carefully reviewing the results.”