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Law enforcement agencies across the UK effectively campaigned to use a face scanning system acknowledged as discriminatory against females, young people, and individuals from minority ethnic backgrounds, following complaints that a more accurate version generated a reduced number of potential suspects.

The Technology in Practice

British police utilize the police national database (PND) to carry out searches using historical face recognition. This procedure involves comparing a reference photograph of a person of interest against a repository of more than 19 million custody photos to identify possible hits.

Admitted Bias

The UK interior ministry admitted last week that the technology was flawed. This admission followed a review by the National Physical Laboratory (NPL) found it misidentified Black and Asian people and females at significantly higher rates than Caucasian males. The Home Office said it “took steps on the findings”.

“It prompts the question of whether this technology only becomes useful if users accept biases in ethnicity and gender. Operational ease is a weak argument for disregarding basic freedoms.”

Known Issue

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

Police bosses were informed of the system's bias in late 2024. The government-ordered NPL review concluded the system was more likely to produce false positives for photos of females, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In reaction, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for possible hits be increased to a level where the disparity was greatly diminished.

However, this decision was overturned the following month following complaints from police that the adjusted system was producing a lower number of “investigative leads”. Internal records indicate the stricter setting reduced the number of queries that yielded potential matches from 56% to a mere 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what threshold is now in operation, the recent NPL study discovered the system could produce false positives for women of Black heritage almost 100 times more often than for white women at specific configurations.

The ministry stated on these findings: “Our evaluation found that in a specific scenarios the algorithm is has a greater tendency to wrongly flag some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Describing the impact of the brief increase to the system's confidence threshold, the police records note: “This adjustment significantly reduces the effect of discrimination across legally safeguarded attributes of race, age and sex but had a substantially detrimental effect on police efficiency”. The papers further note that forces argued that “a once effective tactic now delivered outcomes of limited benefit”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month public review on its proposals to expand the use of biometric scanning systems. The minister for police the relevant minister has described the technology as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, head of the independent scrutiny and oversight board for the national policing equality strategy, commented: “There was scant consideration in equality strategy sessions of the technology deployment despite clear relevance with the strategy's goals.

“These revelations demonstrate once again that the anti-racism commitments the police has made through the equality initiative are failing to be integrated into wider practice. Our reports have cautioned that new technologies are being implemented in a landscape where racial disparities, inadequate oversight and faulty information gathering continue to exist.

“Any use of this technology must adhere to strict national standards, be subject to external review, and demonstrate it diminishes rather than exacerbates ethnic bias.”

Official Statement

A government representative said: “The Home Office treat the conclusions of the report with utmost gravity and we have already taken action. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be trialled in the coming months and will be subject to further assessment.

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