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Law enforcement agencies across the United Kingdom successfully lobbied to use a face scanning system known to be discriminatory against females, youths, and individuals from ethnic minority groups, after complaining that a less biased version produced fewer potential suspects.

The Technology in Practice

British police use the police national database (PND) to carry out retrospective facial recognition searches. This procedure involves comparing a “probe image” of a person of interest against a repository of over 19 million custody photos to find possible hits.

Admitted Bias

The Home Office admitted last week that the system was biased. This acknowledgment came after a study by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and women at significantly higher rates than Caucasian males. The Home Office said it “took steps on the findings”.

“It prompts the question of whether facial recognition only becomes useful if users tolerate discrimination in ethnicity and sex. Convenience is a poor argument for disregarding fundamental rights.”

Long-Standing Problem

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

Police bosses were notified of the algorithmic discrimination in late 2024. The government-ordered NPL review concluded the system was had a higher probability to suggest incorrect matches for images depicting women, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for possible hits be increased to a point where the bias was significantly reduced.

However, this directive was overturned the next month after forces complained that the modified technology was generating fewer “investigative leads”. NPCC documents show the higher threshold cut the proportion of searches that yielded possible identifications from over half to a just 14%.

Severe Disparities

Although the authorities refused to say what threshold is now in operation, the latest NPL study discovered the system could produce false positives for Black women nearly a hundred times more often than for Caucasian women at specific configurations.

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

Balancing Utility and Fairness

Outlining the impact of the temporary raise to the system's confidence threshold, the police records note: “The change greatly lessens the impact of discrimination across protected characteristics of race, age and sex but had a substantially detrimental effect on operational effectiveness”. The documents add that forces argued that “a previously useful tool now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has launched a ten-week public review on its proposals to expand the use of facial recognition technology. Policing minister Sarah Jones has described the tool as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the advisory panel for the national policing equality strategy, said: “There was very little consideration in equality strategy sessions of the facial recognition rollout despite obvious cross-over with the plan’s concerns.

“This disclosure show yet again that the anti-racism commitments policing has made via 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 context where ethnic inequalities, inadequate oversight and poor data collection already persist.

“All deployment of facial recognition must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it reduces rather than exacerbates racial disparity.”

Home Office Response

A Home Office spokesperson stated: “We treat the findings of the study seriously and we have already taken action. A updated software has been externally evaluated and procured, which has demonstrated no measurable discrimination. It will be trialled early next year 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 each stage of the procedure and no further action would be pursued without trained officers carefully reviewing the output.”