Police forces across the UK successfully lobbied to use a face scanning system known to be biased against females, youths, and individuals from ethnic minority groups, after complaining that a more accurate version produced a reduced number of investigative leads.
British police use the national police database to conduct searches using historical face recognition. This process entails comparing a “probe image” of a suspect against a database of over 19 million custody photos to identify possible hits.
The UK interior ministry admitted last week that the system was flawed. This acknowledgment followed a study by the government's National Physical Laboratory determined it incorrectly matched people of Black and Asian heritage and females at much greater frequency than white men. The ministry stated it “had acted on the findings”.
“It prompts the question of whether facial recognition only becomes useful if users tolerate biases in ethnicity and sex. Operational ease is a weak argument for disregarding basic freedoms.”
Internal documents show 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 mitigate the problem.
Senior officers were informed 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 women, individuals of Black ethnicity, and those aged 40 and under.
In reaction, the National Police Chiefs’ Council (NPCC) mandated that the accuracy setting required for potential matches be raised to a level where the bias was greatly diminished.
However, this decision was overturned the following month following complaints from police that the modified technology was producing a lower number of “investigative leads”. NPCC documents indicate the higher threshold reduced the number of searches that yielded possible identifications from 56% to a just under 15%.
Although the Home Office and NPCC refused to say what threshold is now in operation, the recent independent review found the system could produce false positives for women of Black heritage almost 100 times more often than for Caucasian women at specific configurations.
The ministry commented on these results: “Our evaluation found that in a specific scenarios the algorithm is more likely to wrongly flag some demographic groups in its search results.”
Describing the impact of the brief increase to the system's confidence threshold, the police records state: “This adjustment greatly lessens the impact of discrimination across legally safeguarded attributes of ethnicity, age and gender but had a significant negative impact on police efficiency”. The papers further note that police units argued that “a previously useful tool returned outcomes of limited benefit”.
Meanwhile, the government has launched a ten-week public review on its plans 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”.
The chair of a police oversight board, chair of the advisory panel for the police race action plan, commented: “There was very little consideration in equality strategy sessions of the technology deployment even with obvious cross-over with the strategy's goals.
“This disclosure show yet again that the pledges to combat discrimination policing has undertaken through the equality initiative are failing to be integrated into wider practice. Independent assessments have cautioned that innovative tools are being implemented in a context where ethnic inequalities, inadequate oversight and poor data collection continue to exist.
“Any use of facial recognition must meet strict national standards, be independently scrutinised, and prove it diminishes rather than exacerbates racial disparity.”
A Home Office spokesperson said: “We treat the findings of the report with utmost gravity and we have implemented changes. A new algorithm has been externally evaluated and procured, which has no statistically significant bias. It will be trialled in the coming months and will be undergo evaluation.
“Our priority is ensuring public safety. This gamechanging technology will support police to put criminals and rapists behind bars. There is officer review in every step of the procedure and no arrest or charge would be taken without trained officers meticulously examining the output.”
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