British Police Forces Campaign to Use Biased Face Scanning Technology

Law enforcement agencies across the United Kingdom effectively campaigned to use a face scanning system acknowledged as biased against women, youths, and members of ethnic minority groups, after complaining that a less biased version produced fewer potential suspects.

How the System Works

British police utilize the police national database (PND) to conduct searches using historical face recognition. This process entails matching a “probe image” of a person of interest against a database of more than 19 million custody photos to find possible hits.

Admitted Bias

The Home Office conceded last week that the technology was flawed. This admission followed a study by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and women at significantly higher rates than white men. The ministry said it “had acted on the findings”.

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

Known Issue

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

Police bosses were informed of the algorithmic discrimination in September 2024. The government-ordered NPL review concluded the system was had a higher probability to produce false positives for images depicting women, Black people, and those under 40 years old.

A Policy U-Turn

In response, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for possible hits be increased to a point where the disparity was significantly reduced.

However, this directive was reversed the next month following complaints from police that the modified technology was producing a lower number of “investigative leads”. NPCC documents indicate the higher threshold cut the proportion of searches resulting in potential matches from over half to a just under 15%.

Severe Disparities

Although the authorities declined to specify what setting is now in operation, the recent NPL study found the system could generate incorrect matches for women of Black heritage nearly a hundred times more often than for white women at certain settings.

The Home Office commented on these results: “Our evaluation identified that in a specific scenarios the software is more likely to wrongly flag some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Outlining the effect of the temporary raise to the system's accuracy setting, the police records state: “This adjustment significantly reduces the impact of discrimination across protected characteristics of ethnicity, age and sex but had a significant negative impact on operational effectiveness”. The papers add that police units argued that “a once effective tactic now delivered results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a two-and-a-half-month consultation on its plans to expand the use of biometric scanning systems. The minister for police the relevant minister has described the tool as the “biggest breakthrough since genetic fingerprinting”.

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 very little discussion through race action plan meetings of the technology deployment even with obvious cross-over with the strategy's goals.

“This disclosure show once again that the anti-racism commitments policing has made through the race action plan are not being translated into wider practice. Our reports have cautioned that innovative tools are being rolled out in a context where racial disparities, weak scrutiny and faulty information gathering continue to exist.

“All deployment of facial recognition must adhere to rigorous official guidelines, be subject to external review, and demonstrate it reduces rather than compounds racial disparity.”

Home Office Response

A government representative stated: “The Home Office takes the conclusions of the report with utmost gravity and we have already taken action. A updated software has been externally evaluated 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 protecting the public. This revolutionary tool will support officers to apprehend and prosecute offenders. There is officer review in each stage of the process and no further action would be pursued without specialist personnel carefully reviewing the output.”