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Police forces across the United Kingdom effectively campaigned to use a face scanning system acknowledged as biased against women, young people, and members of minority ethnic backgrounds, after complaining that a more accurate version produced fewer investigative leads.

The Technology in Practice

UK forces utilize the national police database to conduct searches using historical face recognition. This process involves comparing a “probe image” of a person of interest against a repository of over 19 million mugshots to identify potential matches.

Acknowledged Discrimination

The UK interior ministry admitted last week that the system was flawed. This acknowledgment followed a study by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and females at much greater frequency than white men. The Home Office stated it “had acted on the findings”.

“This raises the issue of whether this technology only becomes effective if users tolerate discrimination in ethnicity and sex. Operational ease is a poor argument for overriding fundamental rights.”

Known Issue

Internal documents reveal that this discriminatory flaw has been known about for over twelve months. Furthermore, police forces lobbied to reverse an earlier ruling that was designed to address the problem.

Senior officers were informed of the algorithmic discrimination in September 2024. The government-ordered laboratory study concluded the system was more likely to produce false positives for photos of females, Black people, and those under 40 years old.

A Reversed Decision

In reaction, the national police leadership body mandated that the confidence threshold required for possible hits be raised to a point where the bias was significantly reduced.

However, this decision was reversed the following month after forces complained that the modified technology was generating fewer “useful lines of inquiry”. NPCC documents show the higher threshold reduced the proportion of queries resulting in possible identifications from 56% to a mere 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what setting is now in operation, the latest NPL study discovered the system could produce false positives for Black women almost 100 times more often than for Caucasian women at certain settings.

The ministry stated on these findings: “Our evaluation found that in a specific scenarios the software is more likely to wrongly flag some population segments in its match reports.”

Balancing Utility and Fairness

Outlining the effect of the temporary raise to the system's confidence threshold, the NPCC documents note: “The change significantly reduces the effect of discrimination across legally safeguarded attributes of ethnicity, age and gender but had a substantially detrimental effect on operational effectiveness”. The papers add that police units complained that “a once effective tactic now delivered outcomes of limited benefit”.

Wider Implementation Proposals

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

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the national policing equality strategy, commented: “There was very little consideration through equality strategy sessions of the technology deployment despite clear relevance with the strategy's goals.

“These revelations demonstrate yet again that the anti-racism commitments the police has made through the equality initiative are not being translated into wider practice. Our reports have cautioned that new technologies are being rolled out in a landscape where ethnic inequalities, weak scrutiny and poor data collection continue to exist.

“All deployment of this technology must adhere to strict national standards, be independently scrutinised, and demonstrate it reduces rather than compounds racial disparity.”

Home Office Response

A government representative stated: “The Home Office takes the conclusions of the study seriously and we have implemented changes. A new algorithm has been independently tested and procured, which has demonstrated no measurable discrimination. It will be tested early next year and will be subject to further assessment.

“Our priority is ensuring public safety. This gamechanging technology 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 trained officers carefully reviewing the results.”