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Police forces across the United Kingdom successfully lobbied to deploy a facial recognition system known to be biased against women, young people, and individuals from ethnic minority groups, after complaining that a less biased version generated fewer potential suspects.

The Technology in Practice

UK forces use the police national database (PND) to conduct searches using historical face recognition. This process involves matching a reference photograph of a suspect against a database of more than 19 million custody photos to find possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the technology was biased. This admission followed a study by the National Physical Laboratory (NPL) found it incorrectly matched people of Black and Asian heritage and women at significantly higher rates than Caucasian males. The ministry stated it “took steps on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users accept discrimination in race and sex. Operational ease is a poor argument for overriding basic freedoms.”

Known Issue

Official papers show that this bias has been recognized for more than a year. Furthermore, police forces argued to overturn an earlier ruling that was designed to mitigate the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned laboratory study found the system was had a higher probability to suggest false positives for photos of women, Black people, and those under 40 years old.

A Policy U-Turn

In reaction, the national police leadership body ordered that the confidence threshold required for potential matches be increased to a level where the disparity was greatly diminished.

However, this decision was overturned the following month after forces complained that the modified technology was generating a lower number of “useful lines of inquiry”. NPCC documents indicate the higher threshold cut the proportion of queries resulting in potential matches from over half to a mere 14%.

Severe Disparities

Although the authorities refused to say what setting is now in operation, the latest NPL study discovered the system could generate false positives for Black women nearly a hundred times more frequently than for Caucasian women at certain settings.

The ministry commented on these results: “The testing identified that in a specific scenarios the algorithm is more likely to incorrectly include some demographic groups in its match reports.”

Operational Effectiveness vs. Bias

Outlining the effect of the brief increase to the system's accuracy setting, the NPCC documents note: “The change greatly lessens the impact of bias across legally safeguarded attributes of ethnicity, generation and gender but had a substantially detrimental effect on operational effectiveness”. The documents further note that police units argued that “a previously useful tool now delivered outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the government has launched a two-and-a-half-month consultation on its plans to widen the use of biometric scanning systems. Policing minister the relevant minister has labeled the tool as the “biggest breakthrough since DNA matching”.

Criticism from Advisors and Monitors

The chair of a police oversight board, head of the independent scrutiny and oversight board for the national policing equality strategy, commented: “We observed scant consideration in equality strategy sessions of the technology deployment despite clear relevance with the strategy's goals.

“This disclosure demonstrate once again that the anti-racism commitments the police has undertaken via the equality initiative are failing to be integrated into broader operations. Independent assessments have warned that innovative tools are being rolled out 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 subject to external review, and prove it diminishes rather than compounds racial disparity.”

Official Statement

A government representative said: “The Home Office treat the findings of the study with utmost gravity and we have already taken action. A updated software has been externally evaluated and acquired, which has no statistically significant bias. It will be tested early next year 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 procedure and no arrest or charge would be pursued without specialist personnel meticulously examining the results.”