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Law enforcement agencies across the UK effectively campaigned to deploy a face scanning system acknowledged as discriminatory against females, young people, and individuals from ethnic minority groups, following complaints that a less biased version produced fewer investigative leads.

The Technology in Practice

British police utilize the police national database (PND) to carry out retrospective facial recognition searches. This process involves matching a “probe image” of a suspect against a database of more than 19 million custody photos to find potential matches.

Admitted Bias

The Home Office admitted last week that the technology was biased. This acknowledgment came after a review by the National Physical Laboratory (NPL) determined 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 race and gender. Operational ease is a poor argument for disregarding fundamental rights.”

Known Issue

Internal documents show that this discriminatory flaw has been known about for more than a year. Furthermore, law enforcement argued to overturn an initial decision that was intended to mitigate the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The government-ordered NPL review found the system was more likely to produce false positives for photos of women, Black people, and those aged 40 and under.

A Reversed Decision

In response, the national police leadership body mandated that the confidence threshold required for possible hits be raised to a point where the disparity was greatly diminished.

However, this directive was reversed the following month after forces complained that the adjusted system was producing a lower number of “useful lines of inquiry”. NPCC documents show the higher threshold reduced the number of searches resulting in possible identifications from over half to a just under 15%.

Severe Disparities

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

The ministry commented on these results: “Our evaluation identified that in a limited set of circumstances the software is more likely to incorrectly include some demographic groups in its match reports.”

Balancing Utility and Fairness

Describing the effect of the temporary raise to the system's confidence threshold, the NPCC documents state: “The change greatly lessens the effect of bias across protected characteristics of ethnicity, generation and sex but had a significant negative impact on operational effectiveness”. The papers further note that police units argued that “a once effective tactic now delivered results of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a ten-week consultation on its proposals to widen the use of biometric scanning systems. The minister for police the relevant minister has labeled the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the advisory panel for the police race action plan, said: “We observed very little discussion in equality strategy sessions of the facial recognition rollout even with clear relevance with the strategy's goals.

“This disclosure demonstrate once again that the pledges to combat discrimination the police has undertaken through the race action plan are failing to be integrated into wider practice. Our reports have warned that innovative tools are being implemented in a context where ethnic inequalities, weak scrutiny and poor data collection continue to exist.

“All deployment of this technology must meet rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than compounds racial disparity.”

Official Statement

A Home Office spokesperson stated: “The Home Office takes the findings of the study seriously and we have already taken action. A new algorithm has been independently tested and procured, which has demonstrated no measurable discrimination. It will be trialled in the coming months and will be undergo evaluation.

“Our priority is protecting the public. This revolutionary tool will assist officers 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.”