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Police forces across the United Kingdom successfully lobbied to deploy a face scanning system known to be biased against women, youths, and individuals from minority ethnic backgrounds, after complaining that a less biased version generated fewer investigative leads.

How the System Works

British police utilize the police national database (PND) to conduct retrospective facial recognition searches. This procedure involves comparing a “probe image” of a person of interest against a database of over 19 million mugshots to find possible hits.

Acknowledged Discrimination

The Home Office conceded last week that the system was flawed. This admission followed a review by the government's National Physical Laboratory determined it misidentified people of Black and Asian heritage and females at much greater frequency than Caucasian males. The Home Office stated it “took steps on the findings”.

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

Known Issue

Internal documents reveal that this bias has been known about for more than a year. Furthermore, police forces lobbied to reverse an initial decision that was intended to address the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The government-ordered NPL review concluded the system was had a higher probability to produce incorrect matches for images depicting women, Black people, and those aged 40 and under.

A Reversed Decision

In response, the national police leadership body mandated that the accuracy setting required for possible hits be increased to a point where the disparity was significantly reduced.

However, this directive was overturned the next month after forces complained that the adjusted system was generating a lower number of “investigative leads”. NPCC documents show the stricter setting reduced the proportion of queries resulting in possible identifications from over half to a mere 14%.

Severe Disparities

Although the Home Office and NPCC refused to say what setting is now in operation, the recent independent review found the system could produce false positives for Black women almost 100 times more frequently than for Caucasian women at certain settings.

The ministry commented on these results: “The testing identified that in a limited set of circumstances the algorithm is more likely to incorrectly include some population segments in its match reports.”

Operational Effectiveness vs. Bias

Describing the impact of the temporary raise to the system's confidence threshold, the NPCC documents note: “This adjustment greatly lessens the impact of bias across protected characteristics of ethnicity, age and sex but had a significant negative impact on operational effectiveness”. The documents add that police units complained that “a previously useful tool returned outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has launched a ten-week consultation on its proposals to expand the use of facial recognition technology. The minister for police the relevant minister 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 advisory panel for the police race action plan, said: “We observed scant consideration in race action plan meetings of the technology deployment despite clear relevance with the strategy's goals.

“This disclosure show once again that the anti-racism commitments the police has made via the race action plan are not being translated into broader operations. Independent assessments have warned that new technologies are being rolled out in a context where racial disparities, weak scrutiny and faulty information gathering continue to exist.

“All deployment of facial recognition must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it diminishes rather than compounds racial disparity.”

Home Office Response

A Home Office spokesperson said: “The Home Office takes the findings of the study with utmost gravity and we have already taken action. A new algorithm has been externally evaluated and acquired, which has no statistically significant bias. It will be tested 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 apprehend and prosecute offenders. There is human involvement in every step of the process and no arrest or charge would be taken without trained officers carefully reviewing the output.”