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Police forces across the UK effectively campaigned to deploy a facial recognition system acknowledged as biased against females, young people, and members of ethnic minority groups, after complaining that a more accurate version produced fewer potential suspects.

The Technology in Practice

British police utilize the national police database to conduct retrospective facial recognition searches. This process involves matching a “probe image” of a suspect against a repository of over 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office admitted last week that the system was biased. This admission came after a study by the National Physical Laboratory (NPL) determined it misidentified people of Black and Asian heritage and females at much greater frequency than Caucasian males. The Home Office stated it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users accept biases in ethnicity and sex. Operational ease is a poor argument for overriding fundamental rights.”

Known Issue

Official papers reveal that this bias has been known about for more than a year. Furthermore, police forces argued to overturn an initial decision that was intended to mitigate the problem.

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

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the accuracy setting required for potential matches be raised to a point where the bias was greatly diminished.

However, this directive was overturned the following month after forces complained that the adjusted system was generating a lower number of “useful lines of inquiry”. NPCC documents indicate the higher threshold reduced the number of searches that yielded possible identifications from 56% to a mere under 15%.

Profound Inequalities

Although the authorities refused to say what threshold is now in operation, the recent NPL study found the system could produce incorrect matches for women of Black heritage almost 100 times more often than for Caucasian women at certain settings.

The Home Office commented on these findings: “The testing found that in a specific scenarios the software is more likely to incorrectly include some population segments in its match reports.”

Balancing Utility and Fairness

Outlining the impact of the brief increase to the system's accuracy setting, the police records note: “The change significantly reduces the effect of discrimination across protected characteristics of race, 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 limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a two-and-a-half-month consultation on its proposals to expand the use of biometric scanning systems. The minister for police the relevant minister has labeled the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “There was very little discussion in race action plan meetings of the technology deployment despite clear relevance with the plan’s concerns.

“These revelations demonstrate yet again that the anti-racism commitments the police has made via the equality initiative are failing to be integrated into broader operations. Our reports have warned that innovative tools are being rolled out in a landscape where ethnic inequalities, inadequate oversight and faulty information gathering already persist.

“All deployment of this technology must meet strict national standards, be subject to external review, and demonstrate it reduces rather than exacerbates ethnic bias.”

Official Statement

A Home Office spokesperson said: “We treat the conclusions of the study seriously and we have already taken action. A new algorithm has been independently tested and procured, which has demonstrated no measurable discrimination. It will be tested in the coming months and will be subject to further assessment.

“Our priority is protecting the public. This revolutionary tool will assist police to apprehend and prosecute offenders. There is human involvement in every step of the process and no further action would be pursued without specialist personnel meticulously examining the output.”