🔗 Share this article

Police forces across the United Kingdom effectively campaigned to deploy a face scanning system acknowledged as biased against women, youths, and individuals from minority ethnic backgrounds, following complaints that a less biased version generated fewer investigative leads.

How the System Works

British police use the national police database to carry out searches using historical face recognition. This process entails comparing a reference photograph of a suspect against a repository of over 19 million custody photos to identify possible hits.

Acknowledged Discrimination

The UK interior ministry admitted last week that the technology was flawed. This admission followed a review by the government's National Physical Laboratory determined it incorrectly matched people of Black and Asian heritage and females at significantly higher rates than Caucasian males. The ministry stated it “had acted on the findings”.

“This raises the question of whether this technology only becomes effective if users tolerate biases in ethnicity and sex. Operational ease is a weak argument for overriding basic freedoms.”

Long-Standing Problem

Internal documents reveal that this bias has been recognized for over twelve months. Furthermore, law enforcement lobbied to reverse an earlier ruling that was intended to mitigate the problem.

Senior officers were notified of the algorithmic discrimination in late 2024. The government-ordered NPL review concluded the system was more likely to suggest incorrect matches for images depicting women, Black people, and those aged 40 and under.

A Policy U-Turn

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

However, this directive was reversed the following month after forces complained that the adjusted system was generating a lower number of “investigative leads”. NPCC documents indicate the higher threshold reduced the proportion of queries resulting in possible identifications from over half to a just under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what threshold is now in operation, the recent NPL study found the system could generate false positives for Black women nearly a hundred times more often than for white women at certain settings.

The Home Office commented on these results: “The testing identified that in a specific scenarios the software is has a greater tendency to wrongly flag 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 state: “The change greatly lessens the impact of bias across protected characteristics of ethnicity, generation and gender but had a significant negative impact on police efficiency”. The documents add that forces argued that “a previously useful tool returned results of questionable value”.

Wider Implementation Proposals

Meanwhile, the UK administration has launched a ten-week consultation on its proposals to widen the use of biometric scanning systems. The minister for police the relevant minister has described the tool as the “most significant advance since DNA matching”.

Expert and Oversight Concerns

Abimbola Johnson, chair of the advisory panel for the police race action plan, said: “We observed very little consideration in race action plan meetings of the facial recognition rollout despite obvious cross-over with the plan’s concerns.

“This disclosure demonstrate once again that the pledges to combat discrimination policing has made via the equality initiative are failing to be integrated into broader operations. Independent assessments have warned that innovative tools are being implemented in a landscape where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

“All deployment of this technology must adhere to rigorous official guidelines, be independently scrutinised, and prove it reduces rather than exacerbates racial disparity.”

Home Office Response

A government representative said: “The Home Office takes the conclusions of the study seriously and we have implemented changes. 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 undergo evaluation.

“The foremost aim is ensuring public safety. This gamechanging technology will support officers to apprehend and prosecute offenders. There is human involvement in each stage of the procedure and no arrest or charge would be taken without specialist personnel meticulously examining the output.”