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Police forces across the United Kingdom effectively campaigned to deploy a facial recognition system known to be discriminatory against females, young people, and individuals from ethnic minority groups, after complaining that a more accurate version produced fewer investigative leads.

The Technology in Practice

UK forces use the police national database (PND) to carry out searches using historical face recognition. This process entails matching a reference photograph of a person of interest against a repository of over 19 million mugshots to identify possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the system was flawed. This acknowledgment followed a review by the National Physical Laboratory (NPL) found it incorrectly matched people of Black and Asian heritage and females at significantly higher rates than Caucasian males. The Home Office said it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users accept discrimination in ethnicity and gender. Operational ease is a weak argument for disregarding basic freedoms.”

Long-Standing Problem

Internal documents reveal that this discriminatory flaw 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.

Senior officers were notified of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study concluded the system was more likely to produce false positives for images depicting females, individuals of Black ethnicity, and those under 40 years old.

A Policy U-Turn

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

However, this decision was reversed the next month after forces complained that the adjusted system was producing a lower number of “useful lines of inquiry”. Internal records show the higher threshold cut the number of searches resulting in potential matches from over half to a mere 14%.

Severe Disparities

Although the authorities refused to say what setting is now in operation, the latest independent review found the system could generate incorrect matches for Black women almost 100 times more frequently than for white women at certain settings.

The ministry stated on these findings: “Our evaluation found that in a limited set of circumstances the software is more likely to incorrectly include 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 police records note: “This adjustment greatly lessens the impact of bias across legally safeguarded attributes of ethnicity, generation and sex but had a substantially detrimental effect on police efficiency”. The documents add that forces 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 public review on its plans to expand the use of biometric scanning systems. The minister for police the relevant minister has described the technology as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the advisory panel for the police race action plan, commented: “We observed scant consideration in equality strategy sessions of the technology deployment despite clear relevance with the plan’s concerns.

“This disclosure demonstrate yet again that the pledges to combat discrimination the police has undertaken through the equality initiative are failing to be integrated into wider practice. Our reports have cautioned that innovative tools are being implemented in a landscape where racial disparities, weak scrutiny and poor data collection already persist.

“Any use of this technology must adhere to strict national standards, be independently scrutinised, and demonstrate it reduces rather than compounds ethnic bias.”

Home Office Response

A government representative said: “We takes the findings of the report seriously and we have implemented changes. A new algorithm has been independently tested and acquired, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be subject to evaluation.

“The foremost aim is ensuring public safety. This revolutionary tool will support police to apprehend and prosecute offenders. There is officer review in each stage of the process and no further action would be pursued without trained officers meticulously examining the results.”