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Law enforcement agencies across the United Kingdom successfully lobbied to use a face scanning system acknowledged as biased against females, youths, and members of minority ethnic backgrounds, after complaining that a more accurate version generated a reduced number of potential suspects.

The Technology in Practice

British police use the police national database (PND) to conduct retrospective facial recognition searches. This procedure involves comparing a reference photograph of a person of interest against a repository of more than 19 million custody photos to identify possible hits.

Admitted Bias

The Home Office conceded last week that the technology was flawed. This admission followed a review by the government's National Physical Laboratory determined it incorrectly matched Black and Asian people and females at significantly higher rates than white men. The ministry stated it “took steps on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users tolerate biases in ethnicity and sex. Convenience is a poor argument for disregarding basic freedoms.”

Long-Standing Problem

Internal documents show that this discriminatory flaw has been recognized for over twelve months. Furthermore, law enforcement lobbied to reverse an earlier ruling 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 concluded the system was more likely to produce incorrect matches for photos of women, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

In response, the national police leadership body mandated that the confidence threshold required for possible hits be raised to a level where the bias was greatly diminished.

However, this directive was overturned the next month after forces complained that the adjusted system was generating a lower number of “investigative leads”. NPCC documents show the higher threshold reduced the proportion of queries that yielded potential matches from over half to a mere 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is currently used, the latest independent review discovered the system could produce false positives for women of Black heritage nearly a hundred times more frequently than for white women at specific configurations.

The ministry stated on these findings: “The testing found that in a specific scenarios the algorithm is has a greater tendency to wrongly flag some population segments in its match reports.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the police records note: “This adjustment greatly lessens the impact of bias across protected characteristics of ethnicity, age and sex but had a substantially detrimental effect on police efficiency”. The papers add that police units argued that “a previously useful tool now delivered outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the UK administration has launched a ten-week consultation on its proposals to expand the use of facial recognition technology. Policing minister Sarah Jones has described the technology as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the police race action plan, said: “There was very little consideration through equality strategy sessions of the technology deployment even with obvious cross-over with the plan’s concerns.

“This disclosure demonstrate once again that the anti-racism commitments the police has made via the equality initiative are not being translated into wider practice. Our reports have warned that new technologies are being rolled out in a context where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

“Any use of this technology must meet strict national standards, be independently scrutinised, and prove it reduces rather than compounds racial disparity.”

Home Office Response

A Home Office spokesperson said: “The Home Office takes the conclusions of the report 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 trialled in the coming months and will be undergo evaluation.

“The foremost aim is ensuring public safety. This revolutionary tool will assist officers to apprehend and prosecute offenders. There is human involvement in every step of the process and no arrest or charge would be pursued without trained officers meticulously examining the output.”