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Law enforcement agencies across the UK successfully lobbied to use a facial recognition system known to be discriminatory against women, young people, and individuals from minority ethnic backgrounds, following complaints that a less biased version generated fewer potential suspects.

How the System Works

British police use the police national database (PND) to conduct searches using historical face recognition. This process involves comparing a “probe image” of a suspect against a repository of over 19 million mugshots to find possible hits.

Admitted Bias

The Home Office admitted last week that the technology was biased. This admission came after a study by the National Physical Laboratory (NPL) determined it incorrectly matched Black and Asian people and women at significantly higher rates than white men. The Home Office stated it “took steps on the findings”.

“It prompts the issue of whether this technology only becomes useful if users tolerate biases in ethnicity and gender. Convenience is a weak argument for disregarding basic freedoms.”

Known Issue

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

Police bosses were notified of the system's bias in September 2024. The government-ordered laboratory study concluded the system was more likely to produce incorrect matches for images depicting women, Black people, and those under 40 years old.

A Policy U-Turn

In reaction, the national police leadership body ordered that the accuracy setting required for potential matches be raised 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 producing a lower number of “useful lines of inquiry”. Internal records show the higher threshold reduced the proportion of queries resulting in possible identifications from 56% to a just under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what setting is currently used, the latest NPL study discovered the system could generate incorrect matches for Black women almost 100 times more frequently than for Caucasian women at certain settings.

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

Operational Effectiveness vs. Bias

Describing the impact of the brief increase to the system's confidence threshold, the NPCC documents note: “The change significantly reduces the impact of bias across protected characteristics of ethnicity, generation and sex but had a substantially detrimental effect on operational effectiveness”. The documents further note that police units complained that “a previously useful tool now delivered results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a two-and-a-half-month public review on its proposals to widen the use of facial recognition technology. The minister for police Sarah Jones has described the tool as the “biggest breakthrough since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the police race action plan, said: “We observed very little consideration in race action plan meetings of the facial recognition rollout even with clear relevance with the strategy's goals.

“These revelations show yet again that the pledges to combat discrimination the police has undertaken through the race action plan are not being translated into wider practice. Our reports have cautioned that innovative tools are being rolled out in a landscape where racial disparities, inadequate oversight and faulty information gathering already persist.

“All deployment of facial recognition must adhere to rigorous official guidelines, be subject to external review, and demonstrate it diminishes rather than exacerbates ethnic bias.”

Home Office Response

A Home Office spokesperson stated: “We takes the conclusions of the study with utmost gravity and we have already taken action. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be trialled early next year and will be subject to further assessment.

“Our priority is ensuring public safety. This gamechanging technology will support officers to put criminals and rapists behind bars. There is human involvement in every step of the process and no arrest or charge would be taken without specialist personnel meticulously examining the output.”