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Police forces across the UK successfully lobbied to use a face scanning system known to be biased against women, young people, and individuals from ethnic minority groups, following complaints that a less biased version produced a reduced number of potential suspects.

The Technology in Practice

British police use the police national database (PND) to conduct searches using historical face recognition. This process involves matching a “probe image” of a suspect against a database of over 19 million custody photos to find potential matches.

Admitted Bias

The UK interior ministry conceded last week that the system was biased. This admission followed a review by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and females at significantly higher rates than Caucasian males. The Home Office said it “had acted on the findings”.

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

Known Issue

Official papers show that this discriminatory flaw has been recognized for more than a year. Furthermore, police forces lobbied to reverse an earlier ruling that was designed to mitigate the problem.

Senior officers were notified of the system's bias in late 2024. The government-ordered NPL review concluded the system was had a higher probability to produce false positives for images depicting females, Black people, and those under 40 years old.

A Reversed Decision

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

However, this decision was reversed the following month after forces complained that the adjusted system was producing fewer “useful lines of inquiry”. Internal records indicate the stricter setting cut the number of queries that yielded possible identifications from over half to a mere 14%.

Profound Inequalities

Although the authorities refused to say what setting is currently used, the recent independent review found the system could generate false positives for women of Black heritage almost 100 times more frequently than for white women at specific configurations.

The Home Office commented on these findings: “Our evaluation found that in a specific scenarios the algorithm is more likely to incorrectly include some population segments in its search results.”

Operational Effectiveness vs. Bias

Outlining the impact of the brief increase to the system's confidence threshold, the NPCC documents note: “The change significantly reduces the effect of bias across protected characteristics of race, age and sex but had a significant negative impact on police efficiency”. The documents further note that police units argued that “a previously useful tool now delivered outcomes of questionable value”.

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. Policing minister Sarah Jones has described the technology as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the independent scrutiny and oversight board for the national policing equality strategy, said: “There was very little consideration in equality strategy sessions of the facial recognition rollout despite obvious cross-over with the strategy's goals.

“These revelations show once again that the anti-racism commitments the police has made via the equality initiative are not being translated into broader operations. Our reports have cautioned that new technologies are being rolled out in a landscape where ethnic inequalities, inadequate oversight and poor data collection already persist.

“Any use of this technology must meet strict national standards, be subject to external review, and prove it reduces rather than exacerbates racial disparity.”

Home Office Response

A government representative said: “We treat the conclusions of the study with utmost gravity and we have already taken action. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be trialled early next year and will be subject to further assessment.

“Our priority is protecting the public. This revolutionary tool will support police to apprehend and prosecute offenders. There is human involvement in every step of the procedure and no further action would be pursued without trained officers meticulously examining the output.”