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Police forces across the UK successfully lobbied to deploy a face scanning system acknowledged as discriminatory against females, young people, and individuals from ethnic minority groups, after complaining that a less biased version produced fewer potential suspects.

How the System Works

British police use the police national database (PND) to carry out retrospective facial recognition searches. This process involves comparing a “probe image” of a person of interest against a repository of over 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office conceded last week that the system was flawed. This acknowledgment followed a review by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and women at much greater frequency than white men. The ministry stated it “took steps on the findings”.

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

Known Issue

Official papers reveal that this bias has been recognized for over twelve months. Furthermore, law enforcement lobbied to reverse an initial decision that was intended to address the problem.

Police bosses were notified of the algorithmic discrimination in September 2024. The government-ordered laboratory study found the system was had a higher probability to suggest incorrect matches for images depicting women, Black people, and those aged 40 and under.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for possible hits be increased to a point where the bias was greatly diminished.

However, this decision was overturned the next month after forces complained that the adjusted system was producing fewer “investigative leads”. NPCC documents show the stricter setting cut the proportion of queries that yielded potential matches from over half to a mere under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what setting is currently used, 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 certain settings.

The Home Office commented on these results: “Our evaluation found that in a limited set of circumstances the algorithm is more likely to wrongly flag some population segments in its match reports.”

Operational Effectiveness vs. Bias

Describing the effect of the temporary raise to the system's accuracy setting, the NPCC documents state: “This adjustment significantly reduces the impact of discrimination across legally safeguarded attributes of race, age and gender but had a significant negative impact on operational effectiveness”. The papers add that forces argued that “a once effective tactic now delivered results of limited benefit”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a two-and-a-half-month public review on its proposals to widen the use of biometric scanning systems. The minister for police Sarah Jones has labeled the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

Abimbola Johnson, chair of the advisory panel for the national policing equality strategy, commented: “There was scant consideration in race action plan meetings of the technology deployment despite clear relevance with the strategy's goals.

“These revelations show yet again that the pledges to combat discrimination policing has undertaken through the race action plan are not being translated into broader operations. Our reports have warned that new technologies are being rolled out in a context where ethnic inequalities, weak scrutiny and poor data collection already persist.

“All deployment of facial recognition must meet strict national standards, be subject to external review, and demonstrate it diminishes rather than compounds racial disparity.”

Home Office Response

A government representative stated: “We treat the findings of the report seriously and we have implemented changes. A updated software has been independently tested and acquired, which has demonstrated no measurable discrimination. It will be trialled early next year and will be undergo evaluation.

“Our priority is ensuring public safety. This revolutionary tool will support police to apprehend and prosecute offenders. There is human involvement in each stage of the process and no arrest or charge would be taken without specialist personnel meticulously examining the results.”