🔗 Share this article

Law enforcement agencies across the United Kingdom successfully lobbied to deploy a facial recognition system acknowledged as discriminatory against females, youths, and individuals from minority ethnic backgrounds, following complaints that a less biased version produced a reduced number of investigative leads.

The Technology in Practice

UK forces use the police national database (PND) to conduct retrospective facial recognition searches. This procedure entails matching a reference photograph of a person of interest against a repository of over 19 million custody photos 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 National Physical Laboratory (NPL) determined it misidentified people of Black and Asian heritage and females at significantly higher rates than white men. The ministry said it “had acted on the findings”.

“This raises the question of whether this technology only becomes effective if users accept discrimination in ethnicity and sex. Operational ease is a poor argument for overriding fundamental rights.”

Long-Standing Problem

Internal documents reveal that this bias has been known about for more than a year. Furthermore, police forces lobbied to reverse an earlier ruling that was intended to address the problem.

Senior officers were informed of the system's bias in September 2024. The Home Office-commissioned laboratory study concluded the system was had a higher probability to produce false positives for images depicting women, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In reaction, the national police leadership body ordered that the confidence threshold required for possible hits be increased to a level where the bias was greatly diminished.

However, this directive was reversed the next month after forces complained that the modified technology was producing a lower number of “useful lines of inquiry”. Internal records indicate the higher threshold reduced the proportion of searches resulting in potential matches from over half to a just 14%.

Severe Disparities

Although the authorities refused to say what threshold is currently used, the latest NPL study discovered the system could produce incorrect matches for Black women almost 100 times more frequently than for Caucasian women at specific configurations.

The Home Office commented on these findings: “The testing identified that in a limited set of circumstances the software is has a greater tendency to wrongly flag some population segments in its search results.”

Operational Effectiveness vs. Bias

Describing the effect of the temporary raise to the system's accuracy setting, the NPCC documents state: “The change greatly lessens the effect of bias across legally safeguarded attributes of ethnicity, age and gender but had a substantially detrimental effect on operational effectiveness”. The papers further note that police units argued that “a previously useful tool returned results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has launched a two-and-a-half-month public review on its proposals to expand the use of facial recognition technology. Policing minister the relevant minister has labeled the technology as the “most significant advance since genetic fingerprinting”.

Expert and Oversight Concerns

Abimbola Johnson, head of the advisory panel for the national policing equality strategy, commented: “We observed very little discussion in race action plan meetings of the technology deployment despite obvious cross-over with the strategy's goals.

“These revelations demonstrate once again that the pledges to combat discrimination policing has made via the equality initiative are not being translated into broader operations. Independent assessments have cautioned that new technologies are being implemented in a context where ethnic inequalities, weak scrutiny and poor data collection already persist.

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

Home Office Response

A Home Office spokesperson stated: “The Home Office treat the findings of the study seriously and we have already taken action. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be tested in the coming months and will be subject to further assessment.

“The foremost aim is protecting the public. This gamechanging technology will support police to apprehend and prosecute offenders. There is human involvement in every step of the process and no arrest or charge would be pursued without specialist personnel meticulously examining the results.”