🔗 Share this article

Police forces across the UK successfully lobbied to deploy a face scanning system acknowledged as biased against women, youths, and individuals from minority ethnic backgrounds, after complaining that a more accurate version produced fewer potential suspects.

The Technology in Practice

British police use the national police database to carry out searches using historical face recognition. This process involves comparing a reference photograph of a person of interest against a database of over 19 million custody photos to identify possible hits.

Acknowledged Discrimination

The Home Office admitted last week that the technology was biased. This admission came after a study by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and women at significantly higher rates than Caucasian males. The Home Office said it “had acted on the findings”.

“It prompts the question of whether facial recognition only becomes effective if users accept biases in ethnicity and gender. Convenience is a weak argument for disregarding fundamental rights.”

Known Issue

Official papers show that this bias has been known about for over twelve months. Furthermore, law enforcement lobbied to reverse an initial decision that was designed to mitigate the problem.

Senior officers were notified of the system's bias in late 2024. The Home Office-commissioned laboratory study concluded the system was more likely to produce incorrect matches for photos of females, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the accuracy setting required for potential matches be raised to a point where the bias was greatly diminished.

However, this directive was overturned the following month after forces complained that the adjusted system was producing fewer “useful lines of inquiry”. NPCC documents show the higher threshold reduced the proportion of searches resulting in potential matches from over half to a mere 14%.

Profound Inequalities

Although the authorities declined to specify what threshold is now in operation, the recent NPL study found the system could generate false positives for Black women almost 100 times more frequently than for Caucasian women at specific configurations.

The ministry commented on these results: “Our evaluation found that in a limited set of circumstances the software is more likely to wrongly flag some demographic groups in its search results.”

Balancing Utility and Fairness

Outlining the impact of the temporary raise to the system's confidence threshold, the police records note: “This adjustment significantly reduces the impact of discrimination across protected characteristics of race, age and gender but had a substantially detrimental effect on police efficiency”. The papers add that police units complained that “a once effective tactic returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a ten-week public review on its proposals to widen 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, head of the independent scrutiny and oversight board for the national policing equality strategy, commented: “There was very little discussion through equality strategy sessions of the technology deployment despite clear relevance with the plan’s concerns.

“This disclosure show yet again that the pledges to combat discrimination the police has made via the equality initiative are failing to be integrated into wider practice. Independent assessments have warned that innovative tools are being implemented in a context where racial disparities, inadequate oversight and faulty information gathering already persist.

“Any use of facial recognition must adhere to strict national standards, be independently scrutinised, and demonstrate it diminishes rather than compounds racial disparity.”

Official Statement

A Home Office spokesperson stated: “The Home Office takes the conclusions of the study with utmost gravity and we have implemented changes. A new algorithm has been independently tested and acquired, which has demonstrated no measurable discrimination. It will be tested in the coming months and will be subject to evaluation.

“The foremost aim is protecting the public. This revolutionary tool will assist police to apprehend and prosecute offenders. There is officer review in every step of the process and no arrest or charge would be pursued without trained officers meticulously examining the results.”