🔗 Share this article

Police forces across the UK effectively campaigned to use a facial recognition system known to be biased against females, youths, and individuals from minority ethnic backgrounds, after complaining that a more accurate version produced a reduced number of potential suspects.

The Technology in Practice

UK forces utilize the national police database to carry out searches using historical face recognition. This process entails matching a “probe image” of a suspect against a repository of more than 19 million mugshots to find potential matches.

Admitted Bias

The UK interior ministry admitted last week that the technology was flawed. This admission followed a study by the government's National Physical Laboratory determined it misidentified Black and Asian people and females at much greater frequency than white men. The Home Office said it “had acted on the findings”.

“It prompts the question of whether facial recognition only becomes useful if users accept discrimination in race and gender. Operational ease is a poor argument for disregarding fundamental rights.”

Known Issue

Official papers reveal 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.

Police bosses were informed of the system's bias in September 2024. The government-ordered NPL review concluded the system was more likely to suggest false positives for images depicting women, individuals of Black ethnicity, and those under 40 years old.

A Reversed Decision

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

However, this decision was reversed the next month after forces complained that the modified technology was generating a lower number of “investigative leads”. NPCC documents show the stricter setting cut the proportion of searches resulting in possible identifications from 56% to a just under 15%.

Severe Disparities

Although the authorities declined to specify what setting is currently used, the latest independent review discovered the system could generate false positives for Black women almost 100 times more often than for white women at certain settings.

The Home Office commented on these findings: “Our evaluation found that in a specific scenarios the software is has a greater tendency to wrongly flag some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Describing the impact of the brief increase to the system's confidence threshold, the NPCC documents note: “The change significantly reduces the impact of bias across legally safeguarded attributes of ethnicity, age and gender but had a significant negative impact on police efficiency”. The documents add that police units complained that “a previously useful tool now delivered results of questionable value”.

Broader Rollout Plans

Meanwhile, the government has opened a ten-week consultation on its plans to expand the use of biometric scanning systems. Policing minister Sarah Jones has labeled the tool as the “most significant advance since genetic fingerprinting”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the advisory panel for the national policing equality strategy, said: “We observed scant consideration in equality strategy sessions of the facial recognition rollout even with obvious cross-over with the strategy's goals.

“This disclosure show once again that the pledges to combat discrimination the police has undertaken through the equality initiative are not being translated into wider practice. Independent assessments have cautioned that innovative tools are being implemented in a context where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

“All deployment of facial recognition must meet rigorous official guidelines, be independently scrutinised, and prove it reduces rather than compounds ethnic bias.”

Home Office Response

A government representative stated: “We treat the findings of the study with utmost gravity and we have implemented changes. A updated software has been externally evaluated and acquired, which has no statistically significant bias. It will be trialled early next year and will be subject to further assessment.

“Our priority is protecting the public. This gamechanging technology will support officers to apprehend and prosecute offenders. There is human involvement in each stage of the process and no arrest or charge would be taken without trained officers meticulously examining the output.”