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Police forces across the United Kingdom successfully lobbied to use a face scanning system known to be biased against females, youths, and individuals from ethnic minority groups, after complaining that a less biased version produced fewer investigative leads.

How the System Works

British police use the police national database (PND) to conduct searches using historical face recognition. This procedure involves matching a “probe image” of a person of interest against a repository of over 19 million custody photos to find possible hits.

Acknowledged Discrimination

The Home Office admitted last week that the technology was biased. This admission followed a review by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and women at much greater frequency than white men. The Home Office stated it “took steps on the findings”.

“It prompts the issue of whether facial recognition only becomes effective if users accept biases in ethnicity and gender. Convenience is a weak argument for disregarding basic freedoms.”

Long-Standing Problem

Internal documents reveal that this discriminatory flaw has been known about for over twelve months. Furthermore, law enforcement argued to overturn an initial decision that was intended to mitigate the problem.

Police bosses were informed 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, 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 reversed the next month following complaints from police that the modified technology was generating fewer “useful lines of inquiry”. Internal records show the higher threshold reduced the proportion of searches that yielded possible identifications from 56% to a mere under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is now in operation, the latest independent review found the system could produce false positives for women of Black heritage almost 100 times more frequently than for Caucasian women at specific configurations.

The ministry stated on these results: “Our evaluation identified that in a limited set of circumstances the algorithm is has a greater tendency to incorrectly include some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Describing the impact of the brief increase to the system's confidence threshold, the police records state: “This adjustment 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 add that forces argued that “a once effective tactic returned results of limited benefit”.

Broader Rollout Plans

Meanwhile, the UK administration has launched a ten-week public review on its proposals to widen the use of facial recognition technology. The minister for police Sarah Jones has labeled the tool as the “biggest breakthrough since genetic fingerprinting”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “We observed very little discussion in equality strategy sessions of the facial recognition rollout even with obvious cross-over with the plan’s concerns.

“This disclosure show once again that the anti-racism commitments the police has undertaken via the equality initiative are failing to be integrated into broader operations. Our reports have cautioned that new technologies are being implemented in a context where racial disparities, weak scrutiny and faulty information gathering already persist.

“Any use of facial recognition must meet rigorous official guidelines, be subject to external review, and demonstrate it diminishes rather than compounds ethnic bias.”

Official Statement

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

“Our priority is protecting the public. This revolutionary tool will support police to put criminals and rapists behind bars. There is officer review in each stage of the procedure and no further action would be taken without specialist personnel carefully reviewing the results.”