UK Law Enforcement Agencies Lobbied to Employ Discriminatory Face Scanning Systems

Police forces across the UK successfully lobbied to use a face scanning system known to be biased against women, youths, and members of minority ethnic backgrounds, following complaints that a more accurate version produced a reduced number of investigative leads.

The Technology in Practice

UK forces utilize the police national database (PND) to carry out retrospective facial recognition searches. This process entails matching a “probe image” of a person of interest against a repository of over 19 million custody photos to find potential matches.

Admitted Bias

The UK interior ministry admitted last week that the technology was biased. This acknowledgment came after a study by the National Physical Laboratory (NPL) found it incorrectly matched Black and Asian people and women at significantly higher rates than white men. The Home Office said it “took steps on the findings”.

“This raises the issue of whether facial recognition only becomes useful if users accept discrimination in ethnicity and sex. Operational ease 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 argued to overturn an initial decision that was designed to address the problem.

Senior officers were notified of the algorithmic discrimination in September 2024. The government-ordered laboratory study concluded the system was more likely to suggest false positives for photos of females, individuals of Black ethnicity, and those aged 40 and under.

A Reversed Decision

In response, the National Police Chiefs’ Council (NPCC) mandated that the confidence threshold required for possible hits be raised 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 generating a lower number of “investigative leads”. NPCC documents indicate the stricter setting cut the number of queries resulting in possible identifications from over half to a mere under 15%.

Profound Inequalities

Although the Home Office and NPCC refused to say what setting is currently used, the recent NPL study discovered the system could produce incorrect matches for Black women almost 100 times more frequently than for Caucasian women at certain settings.

The ministry stated on these results: “Our evaluation found that in a specific scenarios the software is more likely to incorrectly include some demographic groups in its search results.”

Operational Effectiveness vs. Bias

Outlining the effect of the temporary raise to the system's confidence threshold, the NPCC documents note: “The change significantly reduces the effect of bias across protected characteristics of ethnicity, generation and gender but had a substantially detrimental effect on police efficiency”. The papers add that police units complained that “a previously useful tool returned outcomes of questionable value”.

Broader Rollout Plans

Meanwhile, the UK administration has opened a two-and-a-half-month public review on its proposals to widen the use of biometric scanning systems. Policing minister the relevant minister has described the tool as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the national policing equality strategy, said: “We observed scant consideration in equality strategy sessions of the facial recognition rollout even with clear relevance with the strategy's goals.

“These revelations demonstrate yet again that the anti-racism commitments the police has made through the equality initiative are failing to be integrated into wider practice. Our reports have warned that new technologies are being implemented in a landscape where ethnic inequalities, inadequate oversight and poor data collection continue to exist.

“Any use of this technology must meet strict national standards, be subject to external review, and demonstrate it diminishes rather than compounds ethnic bias.”

Official Statement

A Home Office spokesperson stated: “The Home Office treat the findings of the study with utmost gravity and we have already taken action. A updated software has been independently tested and acquired, which has no statistically significant bias. It will be tested early next year and will be subject to evaluation.

“The foremost aim is ensuring public safety. This gamechanging technology will assist police to apprehend and prosecute offenders. There is human involvement in each stage of the process and no further action would be taken without trained officers meticulously examining the results.”