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Law enforcement agencies across the United Kingdom successfully lobbied to deploy a face scanning system known to be biased against females, young people, and members of ethnic minority groups, after complaining that a less biased version produced fewer investigative leads.

How the System Works

British police use the police national database (PND) to conduct searches using historical face recognition. This process involves matching a “probe image” of a suspect against a repository of over 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) found it misidentified people of Black and Asian heritage and females at significantly higher rates than white men. The Home Office said it “took steps on the findings”.

“It prompts the question of whether this technology only becomes effective if users accept discrimination in ethnicity and gender. Operational ease is a weak argument for disregarding fundamental rights.”

Long-Standing Problem

Internal documents show that this bias has been recognized for more than a year. Furthermore, law enforcement argued to overturn an initial decision that was intended to mitigate the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned NPL review found the system was had a higher probability to produce false positives for photos of females, Black people, and those aged 40 and under.

A Reversed Decision

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

However, this directive was overturned the following month following complaints from police that the modified technology was generating a lower number of “useful lines of inquiry”. Internal records indicate the higher threshold reduced the proportion of queries resulting in possible identifications from 56% to a just 14%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold 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 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 incorrectly include some demographic groups in its match reports.”

Balancing Utility and Fairness

Outlining the effect of the brief increase to the system's accuracy setting, the police records state: “The change greatly lessens the impact of bias across legally safeguarded attributes of race, age and sex but had a significant negative impact on police efficiency”. The documents further note that forces argued that “a previously useful tool now delivered results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a ten-week 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 DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the national policing equality strategy, commented: “There was very little discussion through race action plan meetings of the facial recognition rollout despite clear relevance with the plan’s concerns.

“These revelations demonstrate yet again that the pledges to combat discrimination policing has made via the equality initiative are failing to be integrated into broader operations. Independent assessments have cautioned that innovative tools are being rolled out in a landscape where racial disparities, inadequate oversight and faulty information gathering continue to exist.

“Any use of this technology must adhere to rigorous official guidelines, be subject to external review, and demonstrate it reduces rather than compounds ethnic bias.”

Official Statement

A government representative said: “The Home Office treat the conclusions of the study with utmost gravity and we have already taken action. A updated software has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be subject to further assessment.

“Our priority is ensuring public safety. This revolutionary tool will assist officers to put criminals and rapists behind bars. There is human involvement in every step of the process and no further action would be pursued without specialist personnel carefully reviewing the output.”