🔗 Share this article

Police forces across the UK effectively campaigned to deploy a face scanning system known to be discriminatory against women, youths, and members of minority ethnic backgrounds, following complaints that a less biased version produced fewer potential suspects.

The Technology in Practice

UK forces utilize the police national database (PND) to carry out searches using historical face recognition. This process entails comparing a reference photograph of a suspect against a database of more than 19 million mugshots to find possible hits.

Acknowledged Discrimination

The UK interior ministry admitted last week that the system was biased. This admission came after a study by the National Physical Laboratory (NPL) determined it misidentified people of Black and Asian heritage and women at much greater frequency than Caucasian males. The Home Office said it “had acted on the findings”.

“This raises the issue of whether facial recognition only becomes effective if users accept discrimination in race and sex. Convenience is a weak argument for overriding fundamental rights.”

Known Issue

Internal documents show that this bias has been recognized for over twelve months. Furthermore, law enforcement lobbied to reverse an initial decision that was intended to mitigate 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 produce false positives for photos of females, Black people, and those under 40 years old.

A Reversed Decision

In reaction, 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 decision was reversed the following month after forces complained that the adjusted system was producing a lower number of “useful lines of inquiry”. Internal records show the higher threshold cut the number of queries resulting in potential matches from 56% to a just under 15%.

Severe Disparities

Although the Home Office and NPCC refused to say what setting is now in operation, the latest NPL study found the system could produce false positives for Black women nearly a hundred times more often than for Caucasian women at specific configurations.

The ministry stated on these findings: “Our evaluation found that in a specific scenarios the software is more likely to wrongly flag some population segments in its search results.”

Operational Effectiveness vs. Bias

Describing the impact of the brief increase to the system's confidence threshold, the police records state: “This adjustment greatly lessens the effect of discrimination across legally safeguarded attributes of ethnicity, generation and sex but had a substantially detrimental effect on operational effectiveness”. The documents add that police units complained that “a once effective tactic now delivered outcomes of questionable value”.

Wider Implementation Proposals

Meanwhile, the government has launched a two-and-a-half-month consultation on its plans to expand the use of biometric scanning systems. The minister for police Sarah Jones has described the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the independent scrutiny and oversight board for the police race action plan, said: “We observed very little consideration through race action plan meetings of the facial recognition rollout even with obvious cross-over with the plan’s concerns.

“This disclosure show once again that the pledges to combat discrimination the police has made through the race action plan are not being translated into wider practice. Our reports have cautioned that innovative tools are being rolled out in a context where racial disparities, inadequate oversight and poor data collection continue to exist.

“All deployment of this technology must adhere to strict national standards, be subject to external review, and prove it diminishes rather than compounds ethnic bias.”

Home Office Response

A Home Office spokesperson stated: “The Home Office treat the conclusions of the report with utmost gravity and we have implemented changes. A updated software has been independently tested and acquired, which has no statistically significant bias. It will be tested in the coming months and will be undergo evaluation.

“Our priority is ensuring public safety. This revolutionary tool will support officers to apprehend and prosecute offenders. There is officer review in each stage of the procedure and no further action would be pursued without trained officers meticulously examining the results.”