British Law Enforcement Agencies Campaign to Use Biased Face Scanning Systems

Law enforcement agencies across the UK effectively campaigned to deploy a face scanning system known to be biased against women, young people, and individuals from ethnic minority groups, following complaints that a more accurate version produced fewer investigative leads.

How the System Works

British police use the national police database to carry out retrospective facial recognition searches. This process entails matching a “probe image” of a person of interest against a database of more than 19 million mugshots to find possible hits.

Admitted Bias

The Home Office conceded last week that the system was biased. This admission came after a review by the government's National Physical Laboratory found it misidentified people of Black and Asian heritage and females at significantly higher rates than Caucasian males. The ministry stated it “took steps on the findings”.

“It prompts the question of whether this technology only becomes effective if users tolerate biases in race and sex. Operational ease is a weak argument for overriding fundamental rights.”

Long-Standing Problem

Official papers show that this bias has been known about for more than a year. Furthermore, law enforcement argued to overturn an earlier ruling that was intended to address the problem.

Senior officers were notified of the algorithmic discrimination in September 2024. The government-ordered NPL review found the system was had a higher probability to produce false positives for photos of females, Black people, and those under 40 years old.

A Policy U-Turn

In response, the national police leadership body mandated that the accuracy setting required for possible hits be raised to a level where the bias was greatly diminished.

However, this directive was reversed the next month following complaints from police that the modified technology was generating a lower number of “useful lines of inquiry”. Internal records show the stricter setting cut the number of searches that yielded potential matches from over half to a mere under 15%.

Profound Inequalities

Although the authorities refused to say what threshold is currently used, the recent NPL study found the system could generate false positives for women of Black heritage nearly a hundred times more often than for Caucasian women at specific configurations.

The ministry commented on these findings: “Our evaluation identified that in a limited set of circumstances the algorithm is has a greater tendency to wrongly flag some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents note: “This adjustment significantly reduces the impact of bias across protected characteristics of race, age and gender but had a substantially detrimental effect on police efficiency”. The documents further note that police units complained that “a once effective tactic returned results of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has opened a ten-week public review on its plans to expand the use of facial recognition technology. Policing minister the relevant minister has described the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, chair of the advisory panel for the national policing equality strategy, said: “There was scant consideration through equality strategy sessions of the technology deployment despite clear relevance with the plan’s concerns.

“These revelations show yet again that the pledges to combat discrimination the police has made via the equality initiative are not being translated into wider practice. Independent assessments have cautioned that new technologies are being rolled out in a context where ethnic inequalities, weak scrutiny and faulty information gathering already persist.

“Any use of this technology must adhere to strict national standards, be independently scrutinised, and demonstrate it diminishes rather than compounds ethnic bias.”

Official Statement

A government representative stated: “The Home Office treat the findings of the study seriously and we have already taken action. A new algorithm has been externally evaluated and acquired, which has demonstrated no measurable discrimination. It will be trialled early next year and will be subject to further assessment.

“The foremost aim is protecting the public. This gamechanging technology will support police to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no arrest or charge would be pursued without specialist personnel carefully reviewing the results.”