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

The Technology in Practice

British police use the police national database (PND) to carry out searches using historical face recognition. This procedure entails matching a “probe image” of a suspect against a repository of over 19 million custody photos to identify possible hits.

Acknowledged Discrimination

The UK interior ministry admitted last week that the system was biased. This admission followed a review by the National Physical Laboratory (NPL) determined it misidentified 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 question of whether facial recognition only becomes useful if users tolerate discrimination in race and gender. Convenience is a weak argument for disregarding basic freedoms.”

Long-Standing Problem

Official papers show that this discriminatory flaw has been known about for over twelve months. Furthermore, police forces argued to overturn an initial decision that was intended to address the problem.

Senior officers were informed of the algorithmic discrimination in late 2024. The government-ordered NPL review concluded the system was had a higher probability 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 accuracy setting required for possible hits be increased to a point where the disparity was greatly diminished.

However, this decision was overturned the following month after forces complained that the modified technology was generating fewer “investigative leads”. Internal records indicate the stricter setting cut the proportion of queries that yielded possible identifications from over half to a mere under 15%.

Severe Disparities

Although the authorities declined to specify what threshold is currently used, the latest NPL study discovered the system could generate incorrect matches for women of Black heritage almost 100 times more often than for Caucasian women at certain settings.

The ministry commented on these findings: “Our evaluation found that in a limited set of circumstances the software is has a greater tendency 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 note: “The change greatly lessens the effect of bias across protected characteristics of ethnicity, generation and sex but had a significant negative impact on operational effectiveness”. The documents further note that forces argued that “a previously useful tool returned results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a ten-week consultation on its proposals to expand the use of biometric scanning systems. The minister for police the relevant minister has described the tool as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, head of the independent scrutiny and oversight board for the police race action plan, said: “We observed very little discussion through race action plan meetings of the facial recognition rollout despite obvious cross-over with the plan’s concerns.

“This disclosure show once again that the anti-racism commitments policing has undertaken via the equality initiative are not being translated into broader operations. Our reports have warned that innovative tools are being rolled out in a landscape where racial disparities, weak scrutiny and faulty information gathering continue to exist.

“All deployment of facial recognition must meet strict national standards, be independently scrutinised, and demonstrate it diminishes rather than compounds racial disparity.”

Home Office Response

A Home Office spokesperson stated: “We treat the findings of the report 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 trialled in the coming months and will be undergo further assessment.

“Our priority is ensuring public safety. This revolutionary tool will support officers to put criminals and rapists behind bars. There is human involvement in each stage of the procedure and no arrest or charge would be pursued without trained officers carefully reviewing the results.”