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Law enforcement agencies across the United Kingdom successfully lobbied to use a facial recognition system known to be biased against women, youths, and individuals from minority ethnic backgrounds, following complaints that a more accurate version produced a reduced number of potential suspects.

How the System Works

British police use the national police database to conduct retrospective facial recognition searches. This process involves matching a reference photograph of a suspect against a repository of over 19 million mugshots to find possible hits.

Admitted Bias

The Home Office conceded last week that the technology was biased. This acknowledgment came after a study by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and females at significantly higher rates than Caucasian males. The ministry said it “took steps on the findings”.

“This raises the issue of whether facial recognition only becomes effective if users tolerate discrimination in race and sex. Convenience is a poor argument for overriding basic freedoms.”

Known Issue

Internal documents show that this bias has been recognized for over twelve months. Furthermore, police forces argued to overturn an earlier ruling that was designed to mitigate the problem.

Senior officers were notified of the system's bias in late 2024. The Home Office-commissioned NPL review found the system was more likely to produce incorrect matches for photos of females, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In reaction, the national police leadership body ordered that the confidence threshold required for potential matches be increased to a level where the bias was greatly diminished.

However, this directive was overturned the next month following complaints from police that the adjusted system was producing fewer “investigative leads”. Internal records show the stricter setting cut the proportion of queries that yielded possible identifications from over half to a mere 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is now in operation, the recent independent review discovered the system could produce false positives for women of Black heritage almost 100 times more often than for Caucasian women at certain settings.

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

Balancing Utility and Fairness

Describing the impact of the brief increase to the system's confidence threshold, the police records note: “This adjustment significantly reduces the effect of bias across legally safeguarded attributes of race, age and gender but had a significant negative impact on operational effectiveness”. The documents add that forces complained that “a once effective tactic returned outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the government has launched a two-and-a-half-month public review on its proposals to expand the use of facial recognition technology. The minister for police the relevant minister has described the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the national policing equality strategy, said: “We observed very little consideration in race action plan meetings of the facial recognition rollout despite clear relevance with the plan’s concerns.

“This disclosure show yet again that the anti-racism commitments policing has made via the equality initiative are not being translated into wider practice. Our reports have cautioned that innovative tools are being rolled out in a context where racial disparities, inadequate oversight and poor data collection continue to exist.

“Any use of this technology must adhere to rigorous official guidelines, be independently scrutinised, and prove it diminishes rather than exacerbates racial disparity.”

Official Statement

A government representative stated: “The Home Office takes the findings of the study with utmost gravity and we have already taken action. A updated software has been independently tested and procured, which has no statistically significant bias. It will be tested in the coming months and will be subject to evaluation.

“The foremost aim is protecting the public. This gamechanging technology will assist officers to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no arrest or charge would be taken without specialist personnel meticulously examining the results.”