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Law enforcement agencies across the UK successfully lobbied to deploy a facial recognition system acknowledged as discriminatory against women, young people, and individuals from minority ethnic backgrounds, following complaints that a less biased version generated a reduced number of potential suspects.

How the System Works

British police use the police national database (PND) to conduct searches using historical face recognition. This process entails comparing a reference photograph of a suspect against a database of over 19 million custody photos to identify possible hits.

Admitted Bias

The UK interior ministry conceded last week that the system was biased. This admission came after a study by the government's National Physical Laboratory found it misidentified people of Black and Asian heritage and women at significantly higher rates than Caucasian males. The ministry said it “took steps 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 overriding fundamental rights.”

Known Issue

Internal documents show that this bias has been known about for over twelve months. Furthermore, police forces lobbied to reverse an earlier ruling that was intended to address the problem.

Senior officers were notified of the system's bias in September 2024. The government-ordered laboratory study concluded the system was more likely to suggest incorrect matches for photos of women, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

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

However, this decision was overturned the next month following complaints from police that the adjusted system was producing a lower number of “useful lines of inquiry”. NPCC documents indicate the higher threshold reduced the number of queries resulting in potential matches from 56% to a just 14%.

Severe Disparities

Although the Home Office and NPCC declined to specify what threshold is now in operation, the recent NPL study found the system could generate incorrect matches for women of Black heritage almost 100 times more frequently than for Caucasian women at certain settings.

The Home Office stated on these findings: “Our evaluation found that in a limited set of circumstances the software is has a greater tendency to wrongly flag some population segments in its match reports.”

Balancing Utility and Fairness

Outlining the effect of the temporary raise to the system's accuracy setting, the NPCC documents state: “This adjustment significantly reduces the effect of bias across protected characteristics of race, generation and sex but had a substantially detrimental effect on operational effectiveness”. The papers further note that forces argued that “a previously useful tool returned outcomes of limited benefit”.

Wider Implementation Proposals

Meanwhile, the government has opened a two-and-a-half-month consultation on its proposals to expand the use of biometric scanning systems. The minister for police the relevant minister has labeled the tool as the “most significant advance since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the independent scrutiny and oversight board for the police race action plan, commented: “We observed scant consideration through race action plan meetings of the technology deployment despite clear relevance with the plan’s concerns.

“This disclosure demonstrate once 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 implemented in a context where racial disparities, inadequate oversight and faulty information gathering continue to exist.

“Any use of this technology must meet rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than exacerbates ethnic bias.”

Home Office Response

A government representative said: “We takes the conclusions of the report with utmost gravity and we have implemented changes. A updated software has been independently tested and acquired, which has no statistically significant bias. It will be trialled in the coming months and will be undergo further assessment.

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