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Police forces across the United Kingdom successfully lobbied to deploy a facial recognition system known to be discriminatory against women, youths, and members of ethnic minority groups, following complaints that a less biased version produced fewer potential suspects.

The Technology in Practice

UK forces utilize the police national database (PND) to carry out searches using historical face recognition. This procedure involves comparing a “probe image” of a suspect against a repository of over 19 million custody photos to identify possible hits.

Acknowledged Discrimination

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

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

Long-Standing Problem

Internal documents show that this bias has been recognized for more than a year. Furthermore, police forces argued to overturn an initial decision that was designed to address the problem.

Senior officers were informed of the system's bias in September 2024. The Home Office-commissioned NPL review found the system was had a higher probability to produce false positives for images depicting women, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

In reaction, the national police leadership body mandated that the accuracy setting required for potential matches be raised to a level 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 proportion of searches resulting in potential matches from over half to a mere under 15%.

Profound Inequalities

Although the authorities declined to specify what threshold is currently used, the latest NPL study discovered the system could produce incorrect matches for Black women almost 100 times more frequently than for white women at specific configurations.

The ministry commented on these findings: “The testing identified that in a limited set of circumstances the algorithm is more likely to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents state: “This adjustment significantly reduces the effect of discrimination across legally safeguarded attributes of ethnicity, generation and sex but had a substantially detrimental effect on operational effectiveness”. The papers add that forces argued that “a previously useful tool returned outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the UK administration has launched a two-and-a-half-month public review on its plans to widen the use of biometric scanning systems. The minister for police the relevant minister has described the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the police race action plan, said: “We observed scant consideration in race action plan meetings of the technology deployment even with obvious cross-over with the plan’s concerns.

“This disclosure show yet again that the pledges to combat discrimination the police has made through the race action plan are not being translated into broader operations. Independent assessments have warned that innovative tools are being implemented in a landscape where ethnic inequalities, weak scrutiny and poor data collection already persist.

“Any use of this technology must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than exacerbates ethnic bias.”

Home Office Response

A government representative stated: “The Home Office treat the findings of the study seriously and we have implemented changes. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be tested in the coming months and will be subject to evaluation.

“Our priority is protecting the public. This revolutionary tool will support police to apprehend and prosecute offenders. There is human involvement in every step of the process and no arrest or charge would be taken without trained officers carefully reviewing the results.”