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Police forces across the UK effectively campaigned to use a face scanning system acknowledged as biased against females, young people, and members of ethnic minority groups, after complaining that a more accurate version produced a reduced number of potential suspects.

The Technology in Practice

UK forces use the police national database (PND) to carry out searches using historical face recognition. This process entails matching a “probe image” of a suspect against a database of more than 19 million mugshots to find possible hits.

Acknowledged Discrimination

The Home Office admitted last week that the system was flawed. This acknowledgment followed a study by the National Physical Laboratory (NPL) determined it misidentified Black and Asian people and females at significantly higher rates than Caucasian males. The ministry stated it “had acted on the findings”.

“It prompts the issue of whether facial recognition only becomes effective if users accept discrimination in race and sex. Operational ease is a weak argument for overriding basic freedoms.”

Known Issue

Internal documents reveal that this discriminatory flaw has been recognized for more than a year. 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 Home Office-commissioned laboratory study concluded the system was more likely to produce false positives for photos of women, Black people, and those aged 40 and under.

A Reversed Decision

In response, the national police leadership body ordered that the confidence threshold required for potential matches be raised to a point where the bias was greatly diminished.

However, this decision was overturned the next month following complaints from police that the modified technology was generating a lower number of “useful lines of inquiry”. NPCC documents indicate the higher threshold reduced the proportion of searches that yielded possible identifications from over half to a just 14%.

Profound Inequalities

Although the authorities declined to specify what setting is currently used, the recent NPL study found the system could generate incorrect matches for women of Black heritage nearly a hundred times more frequently than for Caucasian women at specific configurations.

The ministry commented on these results: “Our evaluation identified that in a specific scenarios the algorithm is more likely to incorrectly include some population segments in its search results.”

Balancing Utility and Fairness

Outlining the impact of the brief increase to the system's confidence threshold, the police records state: “The change significantly reduces the impact of bias across protected characteristics of ethnicity, age and sex but had a substantially detrimental effect on police efficiency”. The documents add that forces complained that “a previously useful tool returned results of questionable value”.

Broader Rollout Plans

Meanwhile, the UK administration has launched a two-and-a-half-month public review on its proposals to widen the use of facial recognition technology. The minister for police the relevant minister has described the technology as the “biggest breakthrough since DNA matching”.

Expert and Oversight Concerns

The chair of a police oversight board, chair of the advisory panel for the national policing equality strategy, said: “There was scant consideration in equality strategy sessions of the technology deployment even with obvious cross-over with the plan’s concerns.

“This disclosure demonstrate once again that the anti-racism commitments policing has undertaken via the race action plan are not being translated into wider practice. Our reports have cautioned that new technologies are being implemented in a landscape where ethnic inequalities, inadequate oversight and poor data collection already persist.

“All deployment of facial recognition must adhere to rigorous official guidelines, be independently scrutinised, and demonstrate it reduces rather than exacerbates ethnic bias.”

Official Statement

A government representative said: “The Home Office takes the findings of the study seriously and we have implemented changes. A new algorithm has been independently tested and procured, which has no statistically significant bias. It will be trialled early next year and will be subject to further assessment.

“The foremost aim is protecting the public. This revolutionary tool will assist officers to put criminals and rapists behind bars. There is human involvement in every step of the procedure and no further action would be taken without trained officers carefully reviewing the output.”